Developing Assessments for the Next Generation Science Standards (2014)

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ASSESSMENTS TO MEET THE GOALS OF THE FRAMEWORK

The committee’s charge is to recommend best practices for developing reliable and valid assessments that measure student proficiency in science as conceptualized in A Framework for K-12 Science Education: Practices, Crosscutting Concepts, and Core Ideas (National Research Council, 2012a, hereafter referred to as “the framework”) and the Next Generation Science Standards: For States, By States (NGSS Lead States, 2013). In this chapter, we review the main features of these two documents with respect to the assessment challenges they pose.¹

THE FRAMEWORK’S VISION FOR K-12 SCIENCE EDUCATION

There are four key elements of the framework’s vision for science education that will likely require significant change in most science classrooms:

1. a focus on developing students’ understanding of a limited set of core ideas in the disciplines and a set of crosscutting concepts that connect them;
2. an emphasis on how these core ideas develop over time as students’ progress through the K-12 system and how students make connections among ideas from different disciplines;

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¹We refer readers to the framework and the Next Generation Science Standards for a complete picture of what they propose for science education.

3. a definition of learning as engagement in the science and engineering practices to develop, investigate, and use scientific knowledge; and
4. an assertion that science and engineering learning for all students will entail providing the requisite resources and more inclusive and motivating approaches to instruction and assessment, with specific attention to the needs of disadvantaged students.

The framework was built on previous documents that lay out expectations for K-12 learning in science, drawing on ideas developed in National Science Education Standards (National Research Council, 1996), the Benchmarks for Science Literacy (American Association for the Advancement of Science, 1993, 2009), Science Framework for the 2009 National Assessment of Educational Progress (National Assessment Governing Board, 2009), and the Science College Board Standards for College Success (College Board, 2009).

The design of the framework was also influenced by a body of research conducted over the 15 years since the publication of National Science Education Standards (National Research Council, 1996). This research demonstrates that science and engineering involve both knowing and doing; that developing rich, conceptual understanding is more productive for future learning than memorizing discrete facts; and that learning experiences should be designed with coherent progressions over multiple years in mind (see research syntheses in National Research Council, 2006, 2007, 2009; National Academy of Engineering and National Research Council, 2009). Thus, the goal of science education, as articulated in the framework, is to help all students consciously and continually build on and revise their knowledge and abilities through engagement in the practices of science and engineering.

The framework also emphasizes the connections among science, engineering, and technology. Key practices and ideas from engineering are included because of the interconnections between science and engineering and because there is some evidence that engaging in engineering design can help to leverage student learning in science. The goal of including ideas related to engineering, technology, and the applications of science in the framework for science education is not to change or replace current K-12 engineering and technology courses (typically offered only at the high school level as part of career and technical education offerings). Rather, the goal is to strengthen science education by helping students understand the similarities and differences between science and engineering by making the connec-

tions between the two fields explicit and by providing all students with an introduction to engineering.

The concept of equity is integral to the framework’s definition of excellence. The framework’s goals are explicitly intended for all students, and it emphasizes that learners from diverse backgrounds can indeed engage in and learn complex subject matter. The Next Generation Science Standards (NGSS) also highlight issues related to equity and diversity and offer specific guidance for fostering science learning for diverse groups (see NGSS Lead States, 2013, Appendix D). It notes important challenges: students’ opportunities to learn are rarely equitable, and the changes to curriculum and instruction called for may take longest to reach the students already at the greatest disadvantage in science education. Opportunity to learn is a matter not only of resources, such as instructional time, equipment, and materials, and well-prepared teachers; it is also a matter of the degree to which instruction is designed to meet the needs of diverse students and to identify, draw on, and connect with the advantages their diverse experiences give them for learning science. This conception of opportunity to learn will be key to meeting the framework’s vision, as it explicitly notes (NGSS Lead States, 2013, p. 28). There is increasing recognition that the diverse customs and orientations that members of different cultural communities bring to both formal and to informal science learning are assets on which to build. Teachers can connect this rich cultural base to classroom learning by embracing diversity as a means of enhancing learning about science and the world.

Although brief, the above description makes clear the extent of the challenge posed by the framework’s definition of excellence. Assessment designers are faced with the challenge of finding a balance among three competing priorities: (1) using assessment as a tool for supporting and promoting an ambitious vision for all students, (2) obtaining accurate measures of what students have actually learned, and (3) supporting equity of opportunity for disadvantaged students. If the implementation of the NGSS proceeds as intended, then new assessment designs will be developed and implemented in the context of significant changes to all aspects of science education—a circumstance that magnifies the challenge of finding the right balance among the three priorities. And all of these challenges arise in the context of serving all students. The myriad issues associated with meeting these challenges and, more broadly, the framework’s goals of science education for all students, are beyond the committee’s charge. We do, however, highlight ways in which equity issues should be considered in designing assessments. We also discuss diversity issues in greater detail when we turn to implementation in Chapter 7.

DIMENSIONS OF THE FRAMEWORK

The framework is organized by its three primary dimensions: (1) scientific and engineering practices, (2) crosscutting concepts, and (3) disciplinary core ideas: see Box 2-1. This three-part structure signals an important shift for science education and presents the primary challenge for assessment design: to find a way to capture and support students’ developing proficiency along the intertwined dimensions.

Dimension 1: Scientific and Engineering Practices

Dimension 1 identifies eight important practices used by scientists and engineers, such as modeling, developing explanations or solutions, and engaging in argumentation. The framework emphasizes that students need to actively engage in these scientific and engineering practices in order to truly understand the core ideas in the disciplines. The introduction of practices is not a rejection of the importance

of engaging students in inquiry as a component of science learning but rather a clarification that highlights the diversity of what scientists actually do.

The framework asserts that students cannot appreciate the nature of scientific knowledge without directly experiencing and reflecting on the practices that scientists use to investigate and build models and theories about the world. Nor can they appreciate the nature of engineering unless they engage in the practices that engineers use to design and build systems. The opportunity to learn by experiencing and reflecting on these practices, the framework’s authors note is important because it helps students understand that science and engineering are not a matter of applying rote procedures. Engaging in and reflecting on the practices will help students see science as an iterative process of empirical investigation, evaluation of findings, and the development of explanations and solutions. Likewise, it will help students see engineering—a process of developing and improving a solution to a design problem—as both creative and iterative.

Dimension 2: Crosscutting Concepts

The framework identifies seven crosscutting concepts that can help students link knowledge from the various disciplines as they gradually develop a coherent and scientific view of the world. These crosscutting concepts are fundamental to understanding science and engineering, but they have rarely been taught or have not been taught in a way that fosters understanding of their cross-disciplinary utility and importance. Explicit attention to these concepts can help students develop an organizational framework for connecting knowledge across disciplines and developing integrated understanding of what they learn in different settings. The crosscutting concepts will be reinforced when they are addressed in the context of many different disciplinary core ideas. The framework posits that if this is done intentionally, using consistent language across years of schooling, students can come to recognize how the concepts apply in different contexts and begin to use them as tools to examine new problems. The idea that crosscutting concepts are fundamental to understanding science and engineering is not a new idea. Chapter 11 of Science for All Americans could not be clearer about the importance of crosscutting concepts and how they apply across the different areas of science.²

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²See http://www.project2061.org/publications/sfaa/online/chap11.htm [March 2014].

Dimension 3: Disciplinary Core Ideas

The framework identifies disciplinary core ideas for the physical, life, and earth and space sciences and for engineering, technology, and applications of science. The framework makes clear that the purpose of science education is not to teach all the details—an impossible task—but to prepare students with sufficient core knowledge and abilities so that they can acquire and evaluate additional information on their own or as they continue their education.

The dimension of core ideas is extremely important. Education structured around a limited number of core ideas allows the time necessary for students to explore ideas in greater depth at each grade level and engage in the full range of practices. This dimension is in part a practical idea that has gained currency as people have recognized that curricula and standards that cover many details are too broad to provide guidance about priorities and can lead to instruction that is “a mile wide and an inch deep” (Schmidt et al., 1999). Research on science learning also supports the idea that learning should be linked to organizing structures (National Research Council, 2007).

INTEGRATION: THREE-DIMENSIONAL SCIENCE LEARNING

The framework emphasizes that science and engineering education should support the integration of disciplinary core ideas and crosscutting concepts with the practices needed to engage in scientific inquiry and engineering design.³ In this report, we refer to this integration of content knowledge, crosscutting concepts, and practices as “three-dimensional science learning,” or more simply “three-dimensional learning.” That is, during instruction, students’ engagement in the practices should always occur in the context of a core idea and, when possible, should also connect to crosscutting concepts. Both practices and crosscutting ideas are viewed as tools for addressing new problems as well as topics for learning in themselves. Students need to experience the use of these tools in multiple contexts in order to develop the capacity to wield them flexibly and effectively in new problem contexts—an important goal of science learning (National Research Council, 2000, 2007).

To support this kind of science learning, standards, curriculum materials, instruction, and assessments have to integrate all three dimensions. The frame-

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³We note that students cannot engage in all the practices of science and engineering in the ways that scientists and engineers carry them out. Thus, the practices we refer to in this report are approximations of the practices through which scientists and engineers generate and revise their understandings of natural and designed systems.

work thus recommends that standards take the form of performance expectations that specify what students should know and be able to do in terms that clearly blend or coordinate practices with disciplinary core ideas and crosscutting concepts.⁴ Assessment tasks, in turn, have to be designed to provide evidence of students’ ability to use the practices, to apply their understanding of the crosscutting concepts, and to draw on their understanding of specific disciplinary ideas, all in the context of addressing specific problems.

In developing the NGSS, development teams from 26 states and the consultants coordinated by Achieve, Inc., elaborated the framework’s guidelines into a set of performance expectations that include descriptions of the ways in which students at each grade are expected to use both the practices and crosscutting concepts combined with the knowledge they are expected to have of the core ideas. The performance expectations are available in two organizational arrangements, by disciplinary core idea or by topic. Each presents related ideas in such a way that it is possible to read through clusters of performance expectations related to, for example, a particular aspect of a disciplinary core idea at each grade or grade band. Each performance expectation asks students to use a specific practice, and perhaps also a crosscutting concept, in the context of a disciplinary core idea. Across the set of expectations for a given grade level, each practice and each crosscutting idea appears in multiple standards.

To illustrate, Box 2-2 shows performance expectations for 2nd-grade students related to matter and its interactions. The top section (considered the assessable component) lists four performance expectations that describe what 2nd-grade students who demonstrate the desired grade-level understanding in this area know and can do. The three vertical columns below and in the center (called “foundation boxes”) provide the connections to the three dimensions, listing the specific practices students would use and the relevant specific core ideas and crosscutting concepts for this grade level. The text in these boxes expands and explains the performance expectations in terms of each of the three framework dimensions.⁵

The framework argues that disciplinary core ideas should be systematically revisited in new contexts across time to allow students to apply, extend, and develop more sophisticated understanding of them. Instruction should thus care-

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⁴The performance expectations recommended in the framework are based on the model put forward in Science: College Board Standards for College Success (College Board, 2009).

⁵The NGSS also show the connections to performance expectation for other core ideas for the 2nd grade and to related performance expectations for later grade levels, as well as links to elements of the Common Core State Standards in English language arts and mathematics.

fully build ideas across years and between science disciplines. Instead of treating a large number of independent topics, instruction should guide students along pathways through learning progressions. This approach calls for standards, curriculum materials, and assessments that are coherent across time so that they can both help students build increasingly sophisticated understandings of the core ideas across multiple grades and support students in making connections among core ideas in different disciplines.

Learning Progressions: Developing Proficiency Over Time

Research on learning shows that to develop a coherent understanding of scientific explanations of the world, students need sustained opportunities to engage in the practices, work with the underlying ideas, and appreciate the interconnections among these practices and ideas over a period of years, not weeks or months (National Research Council, 2007). Researchers and science educators have applied this insight into how students learn in descriptions of the way understanding of particular content matures over time, called learning progressions. Learning progressions may provide the basis for guidance on the instructional supports and experiences needed for students to make progress (as argued in Gotwals and Songer, 2013; Corcoran et al., 2009; National Research Council, 2007; Smith et al., 2006).

Learning progressions are anchored at one end by what is known about the concepts and reasoning students have as they enter school. At the other end, learning progressions are anchored by societal expectations about what students should understand about science by the end of high school. Learning progressions describe the developing understandings that students need as they progress between these anchor points—the ideas and practices that contribute to building a more mature understanding. They often also address common misunderstandings and describe a continuum of increasing degrees of conceptual sophistication that are common as students if they are exposed to suitable instruction (National Research Council, 2007).

The framework builds on this idea by specifying grade-band endpoint targets at grades 2, 5, 8, and 12 for each component of each core idea. The grade-band endpoints are based on research and on the framework committee’s judgments about grade appropriateness. Most of the progressions described in the NGSS (which are based on the endpoints described in the framework) were not primarily based on empirical research about student learning of specific material because such research is available only for a limited number of topics (see

Corcoran et al., 2009).⁶ Thus, the framework and the NGSS drew on available research, as well as on experience from practice and other research- and practice-based documents (American Association for the Advancement of Science, 2001, 2007; National Research Council, 1996). The NGSS endpoints provide a set of initial hypotheses about the progression of learning for the disciplinary core ideas (National Research Council, 2012a, p. 33). An example, for ideas about how energy for life is derived from food, is shown in Box 2-3.

For the practices and crosscutting concepts, the framework provides sketches of possible progressions for learning each practice or concept, but it does not indicate the expectations at any particular grade level. The NGSS built on those sketches and provide a matrix that defines what each practice might encompass at each grade level, as well as a matrix that defines the expected uses of each

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⁶The American Association for the Advancement of Science (2001, 2007) is another source of progressions of learning that are based on available research supplemented with expert judgment.

crosscutting concept for students at each grade level through 5th grade and in grade bands for middle school and high school.

The progressions in the NGSS are not learning progressions as defined in science education research because they neither articulate the instructional support that would be needed to help students achieve them nor provide a detailed description of students’ developing understanding. (They also do not identify specific assessment targets, as assessment-linked learning progressions do.) However, they are based on the perspective that instruction and assessments must be designed to support and monitor students as they develop increasing sophistication in their ability to use practices, apply crosscutting concepts, and understand core ideas as they progress across the grade levels.

Assessment developers will need to draw on the idea of developing understanding as they structure tasks for different levels and purposes and build this idea into the scoring rubrics for the tasks. The target knowledge at a given grade level may well involve an incomplete or intermediate understanding of the topic or practice. Targeted intermediate understandings can help students build toward a more scientific understanding of a topic or practice, but they may not themselves be fully complete or correct. They are acceptable stepping stones on the pathways students travel between naïve conceptions and scientists’ best current understandings.

Supporting Connections Across Disciplines

A second aspect of coherence in science education lies in the connections among the disciplinary core ideas, such as using understandings about chemical interactions from physical science to explain phenomena in biological contexts. The framework was designed so that when students are working on a particular idea in one discipline, they will already have had experience with the necessary foundational ideas in other disciplines. So, for example, if students are learning about how food is used by organisms in the context of the life sciences in the middle grades, they should already have learned the relevant ideas about chemical transformations in the context of the physical sciences. These connections between ideas in different disciplines are called out in the foundation boxes of the NGSS, which list connections to other disciplinary core ideas at the same grade level, as well as ideas at other grade levels (see Box 2-2, above).

EXAMPLE 1: WHAT IS GOING ON INSIDE ME?

This example of an assessment task illustrates the concept of three-dimensional science learning, the kinds of instructional experiences that are needed to support its development, and the assessment tasks that can provide documentation of this kind of learning.⁷ It also shows how a performance expectation can be used to develop an assessment task and the associated scoring rubric. Specifically, it illustrates how students’ classroom investigations yield products that can be used as formative assessments of their understanding of and ability to connect disciplinary core ideas.

Instructional Context

The curriculum materials for the 7th-grade unit, “What Is Going on Inside Me,” were developed as part of the 3-year middle school curriculum series developed by the Investigating and Questioning our World through Science and Technology (IQWST) project (Krajcik et al., 2008b; Shwartz et al., 2008). IQWST units were designed to involve middle school students in investigation, argumentation, and model building as they explore disciplinary core ideas in depth. IQWST units begin with a driving question, and students investigate phenomena and engage in scientific argumentation to develop explanations through class consensus. In this 7th-grade unit on the human body (Krajcik et al., 2013), the students are on a hunt through the body to find out where the food is going and how the body gets matter and the energy out of that food. Along the way, they also discover that oxygen is required for the production of energy from food.

When students in the middle grades study how food is used, they have to draw on ideas from physical science, such as conservation of matter, transformation of energy, and chemical reactions, if they are to develop the explanatory core idea in the framework. Understanding how energy and matter cycle and flow is a tool for understanding the functioning of any system—so these are crosscutting concepts as well. In this example, the target for learning is not just the idea that humans—like other animals—use food to provide energy, but also a reasoned explanation that the release of this energy must involve a chemical reaction,

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⁷As noted in Chapter 1, we use examples of assessment tasks to illustrate the discussion. This is the first of the seven examples, which are numbered consecutively across Chapters 2, 3, and 4. Like all of our examples, this one is drawn from work done before the framework and the NGSS were available, but the expectations that drove its design are very similar to those in the framework and the NGSS.

and an evidence-based argument for this explanatory account. This explanation requires building knowledge that connects core ideas across several disciplines, from physical sciences to life sciences, as tools to develop and defend the explanation with an argument based on evidence.

In this 8-week investigation, the teacher introduces a general question about what happens inside the body that helps humans do the things they do. The curriculum materials guide students to link this question to their real-world experiences, observations, and activities. Students are expected to develop an explanation for where in the body energy and building materials are obtained from food and how this happens as they progress through all of the activities in the unit.

Teachers support the students through a series of investigations in which pursuing the driving question leads to more specific questions, motivating particular investigations focused on cell growth, what cells need to survive, identifying what materials can get into and out of a cell, and so on. Thus, each step involves questions that teachers develop with their students. Each step helps students incrementally build and extend their model and explanation of the central phenomena as they answer the driving question (Krajcik et al., 2008). Together, they incrementally build evidence and an argument for the explanation that food is broken down and transported through the body to all the cells, where a chemical reaction occurs that uses oxygen and glucose to release energy for use by the cells.

Thus, the question is broadened to also track where the oxygen goes and how it is used, as students notice that increased activity in the body is associated with increased oxygen intake. Tracing of the glucose and the oxygen leads to the conclusion that the food and oxygen are going to all the cells of the body and that is where the energy is released. Teachers support students in figuring out that the only thing that could rearrange the matter in the ways needed and release the energy that the cells appear to be using to do their work is through a chemical reaction. Assembling these arguments depends critically on understandings about energy and chemical reactions that they have developed earlier: see Table 2-1.

Assessment

The assessment portion of the example focuses not only on the important claims students have identified (e.g., that oxygen is used by cells) but also on students’ proficiency with providing an argument for an explanatory mechanism that connects relevant scientific ideas from different disciplines (e.g., a chemical reaction is needed to release stored energy from food, and oxygen is a component of that

TABLE 2-1 Drawing on Prior Principles from Life and Physical Sciences to Construct a Biological Argument That Supports an Explanation for Where and How Oxygen Is Used in the Body

NOTE: LS = life sciences, NGSS DCI = Next Generation Science Standards, Disciplinary Core Ideas, and PS = physical sciences.
SOURCE: Adapted from Krajcik et al. (2013), National Research Council (2012a), and NGSS Lead States (2013).

chemical reaction). In other words, the assessments (described below) are designed to assess three-dimensional learning.

In national field trials of IQWST, 7th- and 8th-grade students were given an assessment task, which was embedded in the curriculum that reflected the performance expectation shown in Box 2-4. When this assessment was given, students had established that food is broken down into glucose and other components and that the circulatory system distributes glucose so that it reaches each cell in the body. Students’ experiments with osmosis had enabled them to conclude that both water and glucose could enter the cell, and experiments with yeast (as a model system for human cells) had led students to establish that cells could use the

glucose for energy and growth, and that this process released waste in the form of carbon dioxide gas. Students had also established that increased energy needs (such as physical activity) are associated with increased consumption of air, and that exhaled air contains proportionally less oxygen than the air in the room.

Students were then asked to synthesize their findings in a written argument in response to the following task (Krajcik et al., 2008b):

Throughout the IQWST curriculum, students learn to write and argue for scientific explanations with a claim, evidence, and reasoning—that is, to incorporate both the construction of an explanation and presentation of an argument for that explanation in their responses (see Berland and Reiser, 2009; McNeill and Krajcik, 2008; Krajcik et al., 2013). Below is a typical response from an 8th-grade student (collected during IQWST field trials) that demonstrates application of the physical science ideas of both energy and matter to explain the oxygen question.

This response shows both what the student currently understands and that he or she drew on evidence from the activity of burning a cashew and thereby heating water. It also illustrates the sort of incomplete target understanding that we have discussed: the student considers the food to contain potential energy but cannot elaborate how the chemical reaction converts the energy to a form cells can use. This conception is acceptable at the middle school level but will need refinement in later grades.

The IQWST materials suggest a scoring rubric for this task: see Box 2-5. The performance expectation and the scoring rubric also show how the assessment measures students’ ability to draw on core ideas from multiple disciplines by asking for an argument and explanation about a phenomenon that requires bringing the physical science understanding to bear on an argument in the biological context. This example shows that, with appropriate prior instruction, students can tackle tasks that assess three-dimensional science learning, that is, tasks that ask them to use science practices in the context of crosscutting concepts and disciplinary core ideas. Furthermore, it shows that classroom engagement in practices (in this case, supporting an explanation with argument from evidence) provides products (in this case, written responses to a probe question) that can be used to evaluate student learning.

CONCLUSIONS

The framework acknowledges that the new vision for science teaching and learning poses challenges for assessment and will require significant changes to current assessment approaches. The example above is the first of several we use to illustrate the specific changes we believe will be needed; it also illustrates that assessment must be considered as part of the overall system of science education. The framework emphasizes the widely shared understanding that the major components of the science education system (curriculum, instruction, teacher development, and assessment) are tightly linked and interdependent, and it advocates a standards-based system that is coherent horizontally (across classrooms at a given grade level), vertically (across levels of control and aggregation of scores, such as across schools, districts, and a state), and developmentally (across grade levels). The framework also follows an earlier report (National Research Council, 2006) in calling for a coherent system of assessments that combines multiple approaches (e.g., including both large-scale and classroom-based assessments) to meet a range of goals (e.g., formative and summative assessments of student learning, program evaluation) in an integrated and effective way. Given the complexity of the assess-

ment challenge, the framework emphasizes that changes will likely need to be phased in over time.

We offer four conclusions about three specific challenges for design and development of assessments to meet the goals of the framework and the NGSS.

Assessing Three-Dimensional Learning

Assessing three-dimensional learning is perhaps the most significant challenge because it calls for assessment tasks that examine students’ performance of a practice at the same time that they are working with disciplinary core ideas and crosscutting concepts. Meeting this challenge can best be accomplished through the use of assessment tasks that comprise multiple related questions, which we refer to as “multicomponent tasks.”

CONCLUSION 2-1 Measuring the three-dimensional science learning called for in the framework and the Next Generation Science Standards requires assessment tasks that examine students’ performance of scientific and engineering practices in the context of crosscutting concepts and disciplinary core ideas. To adequately cover the three dimensions, assessment tasks will generally need to contain multiple components (e.g., a set of interrelated questions). It may be useful to focus on individual practices, core ideas, or crosscutting concepts in the various components of an assessment task, but, together, the components need to support inferences about students’ three-dimensional science learning as described in a given performance expectation.

Assessing the Development of Three-Dimensional Learning Over Time

The framework emphasizes that competence in science develops cumulatively over time and increases in sophistication and power. The framework calls for curricula and instruction that are planned in a coherent way to help students progress along a path toward more sophisticated understanding of core concepts over the course of the entire K-12 grade span. Students’ intermediate steps along this path may not reflect accurate scientific understanding, but they will reflect increasingly sophisticated approximations of scientific explanations of phenomena.

Thus, what needs to be assessed is what point a student has reached along a sequence of progressively more complex understandings of a given core idea, and successively more sophisticated applications of practices and crosscutting concepts. This is a relatively unfamiliar idea in the realm of science assessments, which have more often been designed to measure whether students at a given grade level do or do not

know particular content (facts). To meet this new goal, assessments will have to reflect both what understanding is expected at a particular grade level and the intermediate understandings that may be appropriate at other levels. This idea of intermediate understanding is particularly important for formative or in-class assessment tools (see Chapter 3).

CONCLUSION 2-2 The Next Generation Science Standards require that assessment tasks be designed so that they can accurately locate students along a sequence of progressively more complex understandings of a core idea and successively more sophisticated applications of practices and crosscutting concepts.

Breadth and Depth of Content

The third challenge is to develop assessment tasks that adequately address all elements of all three dimensions and cover all of the performance expectations for a given grade level. The amount of science knowledge specified in the core ideas alone is demanding. The possible ways the ideas might be combined with the practices and crosscutting concepts into performance expectations even for a single grade would yield an even greater range of possible targets for assessment. Moreover, both competence in using the practices and understanding of core ideas need to develop across the grade levels. The NGSS limit the number of performance expectations by choosing to define particular combinations of practices with aspects of a core idea, but there is still a large amount of material to assess. In addition, the time needed for students to undertake the type of multicomponent tasks that can assess a single performance expectation is much greater than the time for a single multiple-choice item testing a particular piece of knowledge.

CONCLUSION 2-3 The Next Generation Science Standards place significant demands on science learning at every grade level. It will not be feasible to assess all of the performance expectations for a given grade level with any one assessment. Students will need multiple—and varied—assessment opportunities to demonstrate their competence on the performance expectations for a given grade level.

The performance expectations in the NGSS help to narrow the scope of what needs to be assessed, but they are complex in terms of the concepts students need to call on in order to demonstrate mastery. Thus, more than one assessment

task may be needed to adequately assess mastery of a given performance expectation, and multiple tasks will be needed to assess the progress of learning all aspects of a particular core idea. We note also that to assess both understanding of core knowledge and facility with a practice, assessments may need to probe students’ use of a given practice in more than one disciplinary context. Furthermore, although the practices are described separately, they generally function in concert, such as when students present an argument based on a model and provide some corroborating evidence in support of an explanation, or when students use mathematics as they analyze data. This overlap means that in some cases assessment tasks may need to be designed around a cluster of related performance expectations. Assessment tasks that attempt to test practices in strict isolation from one another may not be meaningful as assessments of the three-dimensional science learning called for by the NGSS.

CONCLUSION 2-4 Effective evaluation of three-dimensional science learning requires more than a one-to-one mapping between the Next Generation Science Standards (NGSS) performance expectations and assessment tasks. More than one assessment task may be needed to adequately assess students’ mastery of some performance expectations, and any given assessment task may assess aspects of more than one performance expectation. In addition, to assess both understanding of core knowledge and facility with a practice, assessments may need to probe students’ use of a given practice in more than one disciplinary context. Assessment tasks that attempt to test practices in strict isolation from one another may not be meaningful as assessments of the three-dimensional science learning called for by the NGSS.