Current Laboratory Experiences
The previous chapter reviewed research on the outcomes of different types of laboratory experiences and outlined principles of instructional design to guide development of more effective laboratory experiences. In this chapter, the committee reviews evidence about the quantity and quality of laboratory experiences in U.S. high schools today. We begin with a description of the nature of laboratory education, which poses challenges to teachers and schools, and then address how these challenges are being met. The
next section focuses on the amount of time science students spend in laboratory activities as part of their science courses. We then assess current laboratory experiences in light of the range of experiences presented in Chapter 1 and the goals and instructional design principles presented in Chapter 3. The chapter concludes that most laboratory experiences today are “typical” laboratory experiences, isolated from the flow of science instruction. Because these typical laboratory experiences do not follow the design principles we have outlined, they are unlikely to help students attain the science learning goals identified in Chapter 3:
Enhancing mastery of subject matter.
Developing scientific reasoning.
Understanding the complexity and ambiguity of empirical work.
Developing practical skills.
Understanding of the nature of science.
Cultivating interest in science and interest in learning science.
Developing teamwork abilities.
THE UNIQUE NATURE OF LABORATORY EXPERIENCES
Laboratory experiences have features that make them unlike other forms of science instruction. These unique features make it a challenge to structure laboratory experiences so that they neither overwhelm students with complexity on one hand nor rigidly specify all of the questions, procedures, and materials on the other. Over the course of a student’s high school science career, the appropriate balance between complexity and specificity may vary.
Students’ direct interactions with the material world are inherently ambiguous, complex, and messy. Other modes of science instruction, such as lectures, readings, and homework problems, present students with simplified representations of natural phenomena that select and communicate certain variables and attributes (Millar, 2004). Although this simplification is essential for effective learning, it can create distance between classroom learning and real-world applications of science. Students may find that a problem-solving approach that worked well in the classroom fails badly when applied to observation or manipulation of the material world.
Natural phenomena contain much more information than any representation (Millar, 2004), and this wealth of information and complexity can prevent students and teachers from focusing on and attaining the goals of laboratories we have outlined. For example, when discussing a pendulum in class, a physics teacher may ignore without discussion a host of variables that may affect its operation. However, when a student starts doing a simple experiment with a pendulum, these variables suddenly become relevant.
Relevant variables begin with physical forces, including friction and air resistance, and continue through the range of complexity to the air pressure and wind in the room, and they include limits on human reaction time and the acuity of a student’s vision. Along with the enormous increase in the number of possible relevant variables comes the problem of sorting out which ones matter and which do not. This problem can quickly become overwhelming to the student and the instructor.
A student can become frustrated and confused when almost everything seems to matter in a variety of mysterious ways. Should she or he worry about the amount of sound in the room, how warm it is, and whether it is in a basement or on the third floor? The student may feel betrayed by the apparent mismatch between the neatness of a phenomenon as presented in a textbook and the inherent messiness and ambiguity of the same phenomenon encountered in the laboratory. The instructor is similarly confronted with a host of complexities that put enormous demands on both his or her knowledge of the material (and experimental science in general) and ability to turn the student’s confusion and frustration into an educationally valuable experience.
In addition to these problems of frustration and confusion, students sometimes make observations or gather data during laboratory experiences that appear to contradict known scientific principles or concepts (Olsen, Hewson, and Lyons, 1996; Hammer, 1997). To avoid this and to keep students from being overwhelmed by complexity, laboratory manuals and teachers may constrain the types of questions studied and the procedures used to answer these questions (Olsen et al., 1996). Schools and teachers may also respond to these challenges by scheduling fewer or shorter laboratory activities (or eliminating them entirely). The following sections describe current responses to the unique nature of laboratory experiences.
QUANTITY OF LABORATORY INSTRUCTION
The amount of time high school students spend in laboratory experiences is related to the number and level of science courses they take and to the demographics of the school. Students in science courses generally taken after introductory biology and students in schools with fewer non-Asian minorities generally spend more time in laboratory instruction than do students in other science courses and students in schools with high concentrations of non-Asian minorities.
Science Courses and Laboratory Experiences
Over the past 20 years, the percentage of high school graduates taking more than two years of science classes has grown. In 1982, high school gradu-
ates earned an average of 2.2 science credits (1 credit equals 1 year of a course that meets daily). By 1998, the number grew to 3.2 credits. This expansion in the number of science courses taken included all racial/ethnic groups and both male and female students (National Center for Education Statistics, 2004).
The proportion of high school graduates taking science courses after completing general biology has also grown. From 1982 to 2000, the percentage of high school graduates who had completed at least one course beyond general biology increased from 35 to 63 percent, primarily because more students completed introductory chemistry or physics (or both). In 2000, most high school graduates (63 percent) had completed at least one class after taking general biology, 30 percent completed either chemistry or physics, and about 18 percent had completed the highest level classes, which are equivalent to introductory college science courses—advanced placement (AP) and international baccalaureate (IB) biology, chemistry, and physics classes (National Center for Education Statistics, 2004). Other surveys, conducted in conjunction with the National Assessment of Educational Progress (NAEP), found that the fraction of high school graduates who had completed AP or IB science courses increased from 7.8 percent in 1998 to 9.1 percent in 2000 (Perkins, Kleiner, Roey, and Brown, 2004).
Surveys conducted in conjunction with NAEP also indicate that most students do not take four full years of high school science. In response to this survey, 53 percent of 12th graders indicated they were enrolled in a science course. The 12th grade students indicated that most had taken biology in 9th or 10th grade, but fewer had completed chemistry and physics courses in 11th or 12th grade (O’Sullivan, Lauko, Grigg, Quian, and Zhang, 2003).
Features of Current Laboratory Experiences
The available data indicate that the average high school student takes science classes during three of the four years of high school and participates in laboratory activities approximately once a week during these science classes.
Horizon Research, Inc. conducted national surveys of science and mathematics education for the National Science Foundation (NSF) in 1977, 1982, 1993, and 2000 (Smith, Banilower, McMahon, and Weiss, 2002). The surveys included probability samples of schools and teachers, designed to yield nationally representative results, and received high response rates from teachers and principals. Among other questions, the surveys asked about instructional practices (survey results related to laboratory facilities are discussed in Chapter 6).
In response to the year 2000 survey, 71 percent of high school teachers reported that they involved students in “hands-on/laboratory science activities or investigations,” at least once a week, representing a small but statistically significant increase from the 67 percent of high school teachers who reported such activities in 1993. In both 1993 and 2000, high school teachers
reported using about 20 percent of instructional time (about one day a week) for laboratory activities (Smith et al., 2002).
Survey data indicate that many current laboratory experiences are restricted in their settings and use of technology. For example, 50 percent of teachers responding to the 2000 survey indicated that they never took field trips. When the researchers compared national survey results in 1993 and 2000, they found (Smith et al., 2002, p. 43): “the use of computers in science lessons is striking in its lack of change. Even in 2000, less than 10 percent of science lessons included students using computers.”
In 2000, 45 percent of science teachers indicated that they never used laboratory simulations, 54 percent never engaged students in solving problems using simulations, 55 percent never engaged students in collecting data using sensors or probes, and 43 percent never engaged students in retrieving or exchanging data over the Internet. Data collected as part of the NAEP science assessment revealed similarly low levels of technology use in science classrooms (O’Sullivan et al., 2003). It appears that there is a considerable gap between the potential of computer technology to aid student learning in laboratory experiences discussed in Chapter 3 and the current reality.
Disparities in Laboratory Experiences
Variation in Course-Taking
There are racial/ethnic differences in enrollment in the advanced science courses that include more minutes of laboratory instruction. A study of student participation in science courses between 1982 and 1992 found that, at both points in time, black and Hispanic students took fewer science courses than white or Asian students (Quinn, 1996). During most of the 1990s, as high schools offered more science courses, an increasing proportion of students took more advanced courses, but racial/ethnic differences persisted. By 2000, Asians were more likely than students of any other ethnicity to have completed chemistry, physics, and other science courses usually taken after completing general biology, but there was no statistically significant difference in the percentage of white, black, and Hispanic high school graduates who had completed such courses (National Center for Education Statistics, 2004). High school graduates from urban and suburban schools were generally more likely than their counterparts from rural schools to have completed science courses beyond general biology. Participation in AP/IB biology and AP/IB chemistry increased with school size. In addition, as school poverty increased, fewer students completed courses in chemistry and physics (National Science Foundation, 2004).
Data on ethnic group participation in the AP examinations (which most students who enroll in AP courses take) provide indirect evidence of dispari-
ties in enrollment in AP courses. The College Board recently found that white test-takers were roughly proportionate to their representation in the school population as a whole (67.5 percent of the school population and 64.5 percent of AP test-takers). The same was true of Hispanic students, who made up 12.8 percent of the 2004 school population and 13.1 percent of those who took the AP test in 2004. However, black students made up 13.2 percent of the school population but only 6 percent of students who took one or more AP exams in 2004, and American Indians made up 1.1 percent of the school population but only 0.5 percent of AP test-takers. In contrast to these ethnic groups, a disproportionately large share of Asian students took the AP exam (10.6 percent of all AP test-takers) in comparison to their fraction of the total school population (5.1 percent) (College Board, 2005). These data describe the population that took any type of AP test and are not specific to those who took AP science tests.
Science Course Offerings
Variations in patterns of course-taking, especially among poor and minority students, may reflect differences in the kinds of courses offered in schools with different populations of students. For example, one study found that black students enroll in fewer physical science courses, and schools with larger black student populations are likely to offer fewer physical science course opportunities (Norman et al., 2001).
Data on science course offerings gathered in 1990, 1994, and 1998 in conjunction with NAEP show course offerings that vary with the characteristics of schools and students. These data indicate that chemistry, physics, and other science courses usually taken after completing general biology science courses were widely available (90 percent of graduates in all three years attended high schools that offered such courses), but AP and IB courses were less widespread. In 1998, schools attended by 46 percent of graduates offered AP/IB biology, schools attended by 39 percent of graduates offered AP/IB chemistry, and only 27 percent of graduates attended schools offering AP/IB physics (National Science Foundation, 2004). When NSF staff analyzed the survey data, they found that urban and suburban schools, as well as larger schools, more frequently offered advanced science courses than rural schools and smaller schools. They also found that wealthier schools were much more likely to offer AP/IB chemistry and physics classes than schools with high percentages of poor students (National Science Foundation, 2004).
One study found that the availability of AP offerings in California varied with the school’s racial and socioeconomic composition. The availability of AP courses decreased as the percentage of black, Hispanic, or poor students in the school population increased (Oakes et al., 2000).
Although the problem of uneven participation in advanced science courses (and in the laboratory experiences they provide) may be partly explained by inequities in courses offered, other factors are also important. When schools do offer advanced science courses, minority and low-income students are much less likely than other students to enroll in them. (Atanda, 1999; Oakes, 1990; Oakes, Gamoran, and Page, 1992).
Disparities in Laboratory Experiences
Several sources of evidence indicate that the amount of time students spend in laboratory experiences varies based on their ethnicity and level of science courses taken.
A follow-up analysis of data from the 2000 survey of science teachers and schools described above revealed disparities in the frequency and duration of laboratory experiences (Banilower, Green, and Smith, 2004). The authors analyzed data on time spent in various types of science instruction in general and on time spent in various forms of science instruction in the most recent science lesson. For purposes of the study, they grouped the schools included in the survey into four levels of concentration of non-Asian minorities. They found that, during the most recent science lesson, students in schools with the fewest non-Asian minority students spent significantly more time “working with hands-on, manipulative, or laboratory materials” than students in schools with the highest concentration of non-Asian minority students (Banilower et al., 2004, p. 30). They also found that teachers in schools with the second highest and highest concentrations of minority students were significantly more likely than teachers in other schools to engage students in individually reading texts or completing worksheets.
The National Education Longitudinal Study of 1988 analyzed data on high school seniors in 1992 (Quinn, 1996). This study found that the frequency of laboratory experiences varied according to the achievement level of the class (as reported by the teacher). On average, across all classes, 57 minutes per week were allocated for science laboratory activities. Among AP classes, an average of 76 minutes per week was allocated to laboratory activities per week. In low-achievement-level courses, 40 minutes per week was allocated to laboratory activities, compared with 50 minutes per week in average-level classes and 61 minutes for high-achievement-level classes. Other approaches to science instruction also varied by achievement level of the class. In AP courses, a greater percentage of time was spent in whole-class instruction (57 percent) compared with low-achievement classes (47 percent), and less time was spent maintaining order (2 percent of time versus 9 percent of time for low-achievement-level classes). Also, teachers were more likely to lecture in higher achievement level courses, to allow students to respond orally to questions on subject matter, and to use computers. Stu-
dents in the higher achievement classes were less likely to complete individual written assignments or worksheets in class (Quinn, 1996).
In this longitudinal study, Quinn created regression models to explore the relation between socioeconomic status and science teachers’ instructional strategies. When achievement level of the class was not taken into account, students with higher socioeconomic levels received more minutes of laboratory instruction per week. However, when achievement level of the class is taken into account, the effect of socioeconomic status disappeared. A similar effect was obtained for emphasis on inquiry (the processes of science) (Quinn, 1996).
QUALITY OF CURRENT LABORATORY EXPERIENCES
The extent to which current laboratory experiences help students attain educational goals depends not only on how many minutes are spent in laboratory instruction but also on the quality of that instruction.
Comparison with Instructional Design Principles
Research indicates that laboratory experiences are more likely to help students attain learning goals if they are:
designed with clear outcomes in mind,
sequenced into the flow of classroom science instruction,
designed to integrate learning of science content and process, and
incorporated for ongoing student reflection and discussion.
Lack of Focus on Clear Learning Goals
Today’s high school laboratory experiences are not always designed with clear learning outcomes in mind. The effectiveness of a laboratory activity can be assessed in terms of outcomes at two different and interdependent levels, a basic level and the level of desired learning outcomes. In order to be effective in achieving its desired learning outcomes, a laboratory activity must first be effective at the basic level—the students must carry out the activities and obtain the results intended by the designer (Millar, 2004). The inherent complexity and ambiguity of laboratory activities may prevent students from achieving even basic effectiveness. In order to help ensure that they do indeed carry out the activities as intended, laboratory manuals and teachers often provide detailed procedures (Tobin and Gallagher 1987; De Carlo and Rubba, 1994; Priestley, Priestley, and Schmuckler, 1997; Millar,
2004). The resulting “cookbook” activity may reduce the possibility that students’ observations and analysis will lead to conclusions that are at odds with accepted scientific principles, but it may also hamper effectiveness at the higher level (attainment of desired learning outcomes).
When curriculum developers or teachers focus on the goal of foolproof results, they are less likely to design or carry out the laboratory experience with clear learning goals in mind. And, as discussed in the previous chapter, when teachers and students are unclear about the learning goals of laboratory experiences, they are less likely to attain those goals. One experienced high school physics teacher found that several years of providing increasingly detailed instructions helped students in “doing the lab right” (Olsen et al., 1996, p. 785), but it did not help them develop any ideas about the purposes of the laboratory activities.
Isolated from the Flow of Science Instruction
Another problem is that many current laboratory experiences are not well integrated into the stream of instruction (Sutman, Schmuckler, Hilosky, Priestley, and Priestley, 1996). Laboratory activities often remain disconnected and isolated from instruction, rather than being explicitly integrated with lectures, reading, and discussion (Linn, Songer, and Eylon, 1996; Linn, 2003).
Even when laboratory activities are designed in ways that integrate at least partially into the stream of instruction and with clear learning goals in mind, they are not always implemented as planned. The AP Biology Lab Manual for Teachers (College Board, 2001) presents a sequence of five laboratory experiences focusing on diffusion and osmosis. Although this laboratory manual provides no guidance on how to integrate this series of experiences with other forms of instruction or previous biology topics covered, the laboratory experiences themselves are carefully sequenced. The initial two activities engage students in experimenting with dialysis tubing as a model of a cell membrane. In three later activities, students observe osmosis and diffusion in real plant cells, first in a potato core and then in red onion cells. Both this progression of activities and the laboratory manual itself clarify the learning goals for the series (College Board, 2001, p. 1):
investigate the processes of diffusion and osmosis in a model membrane system and
investigate the effect of solute concentration on water potential as it relates to living plant tissues.
These two objectives clearly state the underlying goal of helping students to understand the activity of plant membranes and cells. The lab manual suggests the amount of time needed to complete each activity; following the
BOX 4-1 Diffusion Across a Selectively Permeable Membrane
The laboratory activity is intended to address if the size of a molecule affects whether or not it can diffuse across a selectively permeable membrane. To carry out the experiment, students fill dialysis tubing with a solution of glucose and starch. They place the dialysis tubing in a beaker that contains IKI, a color indicator for starch. Students determine if glucose moves out of the dialysis tubing into the beaker by dipping a test strip into the beaker and checking to see if it changes color (indicating the presence of glucose). Students simultaneously determine if starch crosses this selectively permeable membrane by observing if the color of the water in the beaker changes.
SOURCE: Adapted from <http://www.sc2000.net/~czaremba/aplabs/osmosis.html> and the College Board (2001).
suggestions would require 6-7 periods of science class (assuming a 45-minute class period).
Teachers may not carry out this full sequence of osmosis and diffusion activities, for at least two reasons. First, when they see AP assessments as pressing them to cover multiple science topics, AP school biology teachers may choose to carry out only one or two activities, rather than devoting 6-7 class periods to these topics. Second, teachers and schools who lack funds to purchase the AP biology lab manual can find simplified versions of the first, or the first two, osmosis and diffusion laboratory activities on the Internet at no cost (http://www.ekcsk12.org/science/aplabreview/aplabonediffusionandosmosis.htm and http://www.sc2000.net/~czaremba/aplabs/osmosis.html). These two activities use dialysis tubing as a model of a cell membrane, but neither of the two Internet versions of the activities includes the two learning goals stated in the AP lab manual, which clarify the underlying goal of helping students to understand living plant tissues.
If the first laboratory activity is carried out in isolation from the sequence of other laboratory activities and in isolation from lectures, discussion, and other modes of learning, it may not help students progress in attaining laboratory learning goals (see Box 4-1).
In theory, this experience will enhance students’ understanding of cell membranes and diffusion across cell membranes, which would help achieve
one of the goals of laboratory experiences we have identified—enhancing mastery of subject matter. The activity could theoretically help students attain other goals of laboratory experiences, such as helping them develop scientific reasoning as they gather and interpret their data. Students may also gain an appreciation of the ambiguity and complexity of empirical work if they obtain conflicting results and through discussion are forced to reflect on and consider the sources of these discrepancies. The activity is not specifically designed to teach practical skills or help students develop an understanding of the nature of science.
In practice, this laboratory experience is unlikely to help students attain educational goals unless the teacher can integrate it into the stream of instruction. If the teacher embeds the experiment in instruction on selectively permeable membranes and cells, then it is more likely to help students master this subject matter. If the teacher clarifies the learning goal of the laboratory experience by presenting the dialysis tubing to the student as a model of a cell membrane, then substantially more biological subject matter learning may occur. Similarly, a teacher may decide to ask students to carry out the experiment in two steps, first testing for glucose diffusion and then for starch diffusion. This would eliminate the potential confusion created by testing both starch and glucose diffusion simultaneously. Finally, the teacher may encourage students to discuss among themselves what their results mean and follow up with a whole-class discussion. This opportunity for reflection might help to improve students’ ability to interpret and make inferences from data. Although an expert teacher may focus on desired learning goals and integrate this activity into the curriculum in order to help students attain those goals, teachers often focus instead on the laboratory procedures themselves.
Little Integration of Science Content and Science Process
Current laboratory experiences do not always integrate the learning of science content with learning about the processes of science, perhaps because of the unique challenges presented by laboratory experiences. As noted at the beginning of this chapter, a real pendulum in a high school physics classroom brings with it a host of potentially confusing variables. To reduce the potential confusion and to help students attain one goal—mastery of subject matter—a typical high school pendulum activity is “cleaned up.” This activity is designed to guide students toward making observations that will verify the accepted scientific principle that the period of a pendulum (the time it takes to swing out and back) depends on the length of the string and the force of gravity. It focuses only on science content. Laboratory manuals and teachers rarely use an alternative approach to a pendulum activity designed to help students understand not only this known
principle but also the process scientists use to establish such principles (see Box 4-2).
Although both of these approaches may help students to develop skills in making observations and gathering and presenting data, only the second integrates the learning of science content and process. The first approach is designed to foster students’ mastery of science subject matter, by verifying a known physical relationship. The second approach fosters other goals of the laboratory experience, including understanding the complexity and ambiguity of empirical work, developing scientific reasoning ability, and understanding the nature of science. The second approach is designed to achieve these science process goals in the context of an activity that verifies a known scientific principle, so that it may help students to simultaneously master science subject matter.
Lack of Reflection and Discussion
There is evidence that current laboratory activities rarely incorporate ongoing reflection and discussion, although such discussion can enhance the effectiveness of laboratory learning. Data from the 2000 survey of science teachers indicate that only a third of teachers ask students to present their work once or twice a month, while another 44 percent of teachers use student presentations only a few times each year, although such presentations often lead to discussion and reflection (Weiss, Banilower, McMahon, and Smith, 2001). The survey also indicates that teachers rarely engage students in small-group discussions. A study of laboratory experiences in three high school chemistry classrooms found that the teachers rarely asked the kinds of questions that might generate discussion and reflection on science concepts (DeCarlo and Rubba, 1994); see Box 4-3. In general, the research indicates that students have few opportunities to construct shared understanding of scientific concepts as part of a community of learners in the classroom (Lunetta, 1998).
When discussion does take place during typical laboratory experiences, teachers and students often focus on procedures rather than processes and concepts (Hegarty-Hazel, 1990, cited in Lazarowitz and Tamir, 1994). As a result, students have few opportunities to reflect on and develop their understanding of the scientific concepts underlying their laboratory experiences.
Comparison with a Range of Laboratory Experiences
Over the course of the high school years, a variety of laboratory experiences can help students to experience the range of activities that are part of the work of research scientists. Students’ understanding of the processes of
BOX 4-2 Learning Physics Using a Pendulum: Two Approaches
Most physics textbooks, laboratory manuals, and classrooms include a carefully limited cookbook pendulum activity. Each lab group is given a pendulum with the same mass and is asked to pull the pendulum back the same angle each time and see what happens to the period when the length of the string is changed. The students may even be told to vary the length of the string by increments of 10 cm before each pull. The students are provided with a data chart to fill in the length of the string and the period. The students are then asked to complete a graph of period versus length. When the charts and graphs are filled in, the students hand them in for grading by the teacher.
A few physics texts, laboratory manuals, and teachers take a different approach. The pendulum activity in one curriculum (Hestenes et al., 2002) is designed to develop students’ skills in designing experiments, collecting data, mathematical modeling, and reporting interpretations. Before the laboratory activity, the teacher demonstrates swinging pendulums with at least three different masses and engages students in observing and discussing the behavior of the pendulums. The teacher leads a prelab discussion, helping students identify variables that may affect the period, including variables that cannot be controlled (room temperature, gravity) and variables that can be controlled. Through discussion, the
science can be enhanced when laboratory experiences provide opportunities to:
pose a research question,
use laboratory tools and procedures,
make observations, gather, and analyze data,
verify, test, or evaluate explanatory models (including verifying known scientific theories and laws),
formulate alternative hypotheses,
design investigations, and
build or revise explanatory models.
Few high school students today participate in this full range of laboratory experiences. In response to the 2000 survey of science teachers, 61
teacher helps students identify which controllable variables are related in order to isolate the dependent variable (period) and the independent variables (length, mass, and amplitude). Following a predict-observe-explain approach (see Chapter 3), the teacher asks students to make tentative predictions about how changes in the independent variables will affect the period.
After this discussion, in the laboratory activity, the teacher demonstrates various trials, pulling the pendulums of different masses back at different amplitudes and using different lengths of string. Each student is given a stopwatch to gather data on these trials, and one student records the observations on the blackboard. Students are asked to graph the relationships between period and mass, period and amplitude, and period and length. Following this laboratory activity, the teacher leads a discussion of the importance of adequate data quantity and ranges, modeling, the concepts of dependent and independent variables, and the definitions of period, frequency, weight, and mass. The teacher is told to avoid introducing the formal pendulum equation, because the laboratory activity is not designed to verify this known relationship.
SOURCE: Hestenes, Jackson, Dukerich, and Swackhamer (2002).
percent of high school teachers indicated that they engaged students in hands-on or laboratory science activities once or twice a week, and nearly the same fraction of teachers (59 percent) indicated that students followed specific instructions in an activity or investigation once or twice a week (Banilower et al., 2004). Students are likely to require specific instructions in order to use laboratory tools and procedures, make observations and gather data), while specific instructions would be more difficult to develop and apply to the more complex activities such as formulating a research question and designing an investigation. The frequent use of specific instructions may reflect an emphasis on laboratory experiences that focus on learning to use tools, make observations, and gather data.
Detailed observational case studies and National Research Council (NRC) studies also suggest that current laboratory experiences are primarily restricted to the first three types of opportunities listed earlier. Studies of
BOX 4-3 Examples of High School Chemistry Laboratory Experiences
Two researchers conducted a study of the behavior of three rural Pennsylvania high school chemistry teachers and their students during laboratory activities (DeCarlo and Rubba, 1994). They used a specially designed systematic observation instrument to code teacher and student behaviors during consecutive laboratory activities from November through April. They found that each teacher used a characteristic teaching style throughout this period.
Teacher 1 was highly interactive and social, circulating around the room and talking with students. These conversations usually focused on telling the students what to do or simply on socializing. Teacher 2 was somewhat interactive and somewhat unengaged, and this teacher’s interactions with students were not related to the laboratory activities. Teacher 3 was unengaged, spending most of his time at his desk, where he graded papers, read journals, or did other tasks.
Students of Teacher 1 spent most of the laboratory period manipulating equipment and making observations, and their discussions focused on procedures rather than on interpreting results. Students of Teacher 2 spent most of their time socializing, although they also were engaged in fetching materials, manipulating equipment, and making observations during a few laboratory periods. Students of Teacher 3, like those of Teacher 1, were most frequently engaged in manipulating equipment and making observations. In comparison to students of the other two teachers, students of Teacher 3 were more frequently engaged in discussions related to their laboratory investigations and were less often unengaged in the laboratory activities.
The researchers found that none of the chemistry teachers ever asked questions aimed at encouraging students to think about what they were doing, even though all three had indicated that they did so frequently. In each case, the teachers responded to students’ questions with specific answers, rather than by probing more deeply to understand the reason for the question. Another important finding was that the Teacher 3’s lack of assistance forced the students to think and act on their own, a possibility identified in an earlier study by Shymansky and Penick (1981).
SOURCE: Adapted from DeCarlo and Rubba (1994).
teachers, students, and their interactions have found that teachers tend to emphasize specific instructions (which will help ensure that students’ results verify known scientific principles) even when the teachers have stated that their goal is to stimulate student thinking (DeCarlo and Rubba, 1994; Marx, Freeman, Krajcik, and Blumenfield, 1998). An NRC committee found that high school chemistry laboratory experiences tend more toward verification than problem-solving investigations (National Research Council, 2002, p. 356). Another committee found that laboratory exercises in AP biology courses “tend to be ‘cookbook,’ rather than inquiry based” (National Research Council, 2002, p. 292).1 A recent review of the literature on laboratory education notes that “very often teachers involved students principally in relatively low-level, routine activities in laboratories” (Hofstein and Lunetta, 2004, p. 39).
Frequent laboratory activities emphasizing the use of scientific tools and procedures, gathering data, and verifying known concepts may leave little time for students to formulate research questions, analyze their data, or develop and revise models to explain the data. One study of 12 high school chemistry classes and 26 undergraduate chemistry classes found that there was rarely any follow-up discussion or analysis of data obtained during laboratory activities. In some cases, student groups were asked to combine their data with that of other groups, but the combined data were then never referred to again (Sutman et al., 1996). In response to the 2000 survey, 46 percent of teachers indicated that they asked students to record, represent, or analyze their data once or twice a week and 38 percent asked students to do so once or twice a month. Recording, representing, and analyzing data are essential steps in building and revising explanatory models, but it appears that many laboratory experiences do not include these activities.
In the 2000 survey, only 8 percent of high school teachers indicated that they asked students to design or implement their own investigation once or twice a week. Another 41 percent of teachers said students were asked to design or implement their own investigation once or twice a month; 42 percent of teachers indicated students were asked to design or implement their own investigation a few times a month. As a result, current laboratory experiences may provide few opportunities for students to make progress toward such goals as developing scientific reasoning abilities, understanding the complexity and ambiguity of empirical work, and understanding the nature of science.
What Students Do in Laboratory Experiences
Only a few studies provide detailed descriptions of how students and teachers behave and interact during laboratory experiences. Among these, several focused on the differences between the behavior of boys and girls.
In a study summarizing results from several observational studies of science classes in the United States and Australia, Tobin found that a small group of mostly male “target” students dominated whole-class activities in both high-achieving and low-achieving classes, and they sometimes dominated small group laboratory work as well (Tobin, 1987). In high-achieving classes, the target students were often boys who called out answers during teacher-led lectures, demonstrations, or discussions, while in low-achieving classes, the target students were sometimes those who interrupted the teacher.
Data from the 2000 survey of science and mathematics education indicate that some teachers view the task of managing all the students in large science classes as a challenge. In 2000, 14 percent of high school science program representatives viewed large classes as a serious problem for science instruction, 20 percent said that student absences were a serious problem, and 5 percent indicated that maintaining discipline was a serious problem (Smith et al., 2002).
In Tobin’s observational study, while the teachers focused on responding to or managing the target students, other students rarely asked or answered questions. On the basis of these and other studies, Tobin speculated, “It is entirely likely that high achieving students engage to a greater extent than low achieving students in laboratory activities” (Tobin, 1990, p. 408).
Kelly’s (1988) study of gender differences found that male students actively handle laboratory equipment and supplies more frequently than female students. Kahle, Parker, Rennie, and Riley (1993) found that a small group of male students dominated the use of equipment and also sometimes contaminated reagents or otherwise interfered with equipment and materials. More recently, Jovanovic and King (1998) conducted detailed observations of student behavior in six science classrooms with students in grades 5 through 8. The six classrooms were selected on the basis of a competitive process in which exceptional science teachers were nominated by the Fermi National Accelerator Laboratory Education Office in Batavia, Illinois, based on their expertise in hands-on science teaching. The researchers found that boys and girls were equally likely to actively lead small laboratory groups, but that, as members of the groups, boys more often manipulated equipment while girls more often engaged in such passive behaviors as making suggestions or reading directions. Active leadership was a significant predictor of students’ attitudes toward science and perception of their abilities in science, regardless of gender. Nevertheless, girls’ perceptions of their own
science abilities declined over the course of the year as they engaged in passive behaviors more frequently than boys.
The Jovanovic and King study provides evidence in support of Tobin’s speculation that high-achieving students engage more actively than others in laboratory activities. The authors found a strong correlation between students’ science ability (as measured by a state science assessment) and the frequency of active leadership and equipment manipulation in the laboratory group.
A study of introductory college biology laboratories compared male and female behavior in cookbook laboratory classes with behavior in reformed classes (Russell and French, 2002). In the reformed class, students formed self-selected groups at the beginning of the semester. Before each laboratory period, each student familiarized himself or herself with the activity, developed one or more hypotheses to test, and predicted experimental outcomes. During the laboratory period, the group performed one or more of the planned experiments and wrote a report. The authors of this study conducted detailed observations of students and also surveyed their attitudes and achievement during the semester in which they participated in either the cookbook or the reformed class. They found a positive relationship between time spent manipulating equipment and achievement, as measured by a test of biology content knowledge. They also found that girls participated less frequently in manipulating equipment in both the cookbook and reformed classes, but the gender differences in participation were reduced in the reformed class.
Research evidence on the current laboratory experiences of U.S. high school students is limited. The few studies available provide information on the amount of time students spend in laboratory activities, the goals of these activities, and how teachers and students act during those activities. Findings from these studies, analyzed in light of information on the educational outcomes of laboratory activities, indicate that access to laboratory experiences is uneven, and the quality of current laboratory experiences is poor for most students.
Most science students in U.S. high schools today participate in typical laboratory experiences. Instead of focusing on clear learning goals, teachers and laboratory manuals often emphasize the procedures to be followed, leaving students uncertain about what they are supposed to learn. Lacking a focus on learning goals related to the subject matter being addressed in the science class, current laboratory experiences often fail to integrate student learning about the processes of science with learning about science content. Few current laboratory experiences incorporate ongoing reflection and discussion between and among the teacher and the students, although there is
evidence that such reflection and discussions are essential to help students make meaning out of their laboratory activities. In general, most high school laboratory experiences do not follow the instructional design principles for effectiveness identified by the committee.
Students in schools with higher concentrations of non-Asian minorities spend less time in laboratory instruction than students in other schools, and students in lower level science classes spend less time in laboratory instruction than those enrolled in more advanced science classes. In addition, most high school students participate in a limited range of laboratory activities that do not fully reflect the range of scientists’ activities, limiting opportunities for them to gain understanding of the processes of science.
Laboratory experiences for most high school students today appear to have changed little from those observed by Sutman and colleagues in the mid-1990s. Observing many high school and introductory college laboratory experiences, they found (Sutman et al., 1996, pp. 5-6):
(1) Students experience laboratory based experiences as an add-on to lecture rather than as the “driving force” for later instruction; (2) a very high percentage of the laboratory instructors’ time is spent listening to and responding to students’ procedural questions, with almost no time available for calling upon strategies designed to develop or strengthen higher order thinking. Post-laboratory experiences almost never include follow-up discussion or analysis of the laboratory findings. At the secondary school level laboratory activities were designed to “fit into” or be completed in a designated period of 45 to 90 minutes. There were never additional opportunities for students to extend the basic study. [R]eports of laboratory experiences were graded and returned to students. The reports were never used diagnostically nor did the grades have significance in determining the final course grades.
In the next chapter, we analyze further evidence about factors contributing to the weakness of current laboratory experiences. That chapter contrasts the types of capacity and support teachers need to lead effective laboratory experiences with the limited capacity and support currently available.
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