of instructional time (Linn, 2004). However, in response to opposition, the criteria were changed to require that the instructional materials would comprehensively cover the California science standards with “hands-on activities composing at least 20 to 25 percent of the science instructional program” (California Department of Education, 2004, p. 4, italics added).
The growing variety in laboratory experiences—which may be designed to achieve a variety of different learning outcomes—poses a challenge to resolving these debates. In a recent review of the literature, Hofstein and Lunetta (2004, p. 46) call attention to this variety:
The assumption that laboratory experiences help students understand materials, phenomena, concepts, models and relationships, almost independent of the nature of the laboratory experience, continues to be widespread in spite of sparse data from carefully designed and conducted studies.
As a first step toward understanding the nature of the laboratory experience, the committee developed a definition and a typology of high school science laboratory experiences.
Rapid developments in science, technology, and cognitive research have made the traditional definition of science laboratories—as rooms in which students use special equipment to carry out well-defined procedures—obsolete. The committee gathered information on a wide variety of approaches to laboratory education, arriving at the term “laboratory experiences” to describe teaching and learning that may take place in a laboratory room or in other settings:
Laboratory experiences provide opportunities for students to interact directly with the material world (or with data drawn from the material world), using the tools, data collection techniques, models, and theories of science.
This definition includes the following student activities:
Physical manipulation of the real-world substances or systems under investigation. This may include such activities as chemistry experiments, plant or animal dissections in biology, and investigation of rocks or minerals for identification in earth science.
Interaction with simulations. Physical models have been used throughout the history of science teaching (Lunetta, 1998). Today, students can work