PET Research Base and Philosophy

The PET curriculum is designed from both the constructivist and social-cultural theoretical perspectives1-5 and builds on a conceptual change framework6-7. Student content and nature of science goals are adapted from the middle school physics content and nature of science benchmarks from both the American Association for the Advancement of Science (AAAS) Benchmarks for Scientific Literacy8 and the NRC National Science Education Standards9 (see Standards and Benchmarks).

For each learning goal, PET provides a sequence of activities designed to build on students’ prior knowledge and resources1,10, and to provide sufficient hands-on, computer-based and discussion activities to let them test their initial ideas and guide them towards the development of the target ideas. In the PET classroom, students spend most of their time working in small groups, performing experiments and making sense of their observations, and then sharing ideas in whole class discussions. 

Since students often have difficulty connecting theory with evidence11, each PET activity provides carefully structured questions that help guide students’ thinking (see Structure of Chapters and Activities). The teacher’s role is to guide whole class discussions, help set classroom norms that support evidence-based idea development3, and promote active and substantive participation by all students. 

The quality and variety of experiences from which students can take responsibility for developing each target idea, and both the curricular and professional development support provided for instructors to help them implement the curriculum with high fidelity, were strongly influenced by the Project 2061 Instructional Analysis Criteria12 and the NSES Professional Development Standards7,13.


1 Smith, J.P., diSessa, A., & Roschelle, J. (1993). Misconceptions reconceived: A constructivist analysis of knowledge in transition. Journal of the Learning Sciences, 3(2), 115-163.

von Glasersfeld, E. (1995). Radical constructivism: A way of knowing and learning. Bristol, PA: The Falmer Press.

Cobb, P. & Yackel, E. (1996). Constructivist, emergent, and sociocultural perspectives in the context of developmental research. Educational Psychologist, 31 (3/4), 175-190.

John-Steiner, V. & Mahn, H. (1996). Sociocultural approaches to learning and development: A Vygotskian framework. Educational Psychologist, 31 (3/4), 191-206.

Cobb, P. & Bowers, J. (1999). Cognitive and situated learning perspectives in theory and practice. Educational Researcher, 28 (2), 4-15.

Posner, G. J., Strike, K. A., Hewson, P. W., & Gertzog, W. A. (1982). Accommodation of a scientific conception: Toward a theory of conceptual change. Science Education, 66(2), 211-227.

National Research Council (2000). How people learn: Brain, mind, experience, and school. Washington, D.C.: National Academy Press.

American Association for the Advancement of Science (AAAS) (1993). Benchmarks for science literacy. New York: Oxford University Press.

National Research Council (1995). National science education standards (NSES). Washington DC: National Academy Press.

Hammer, D. (2000). Student resources for learning introductory physics. American Journal of Physics, Physics Education Research Supplement, 68 (S1), S52-S59.

11Carey, S., Evans, R., Honda, M., Jay, E., & Unger, C. (1989). An experiment is when you try it and see if it works: A study of grade 7 students' understanding of the construction of scientific knowledge. International Journal of Science Education, 11, 514-529.

Kesidou, S. and Roseman, J.E., 2002. How Well Do Middle School Science Programs Measure Up? Findings from Project 2061’s Curriculum Review. Journal of Research in Science Teaching,Volume 39, Issue 6, Pages 522-549. For a list of the criteria, see

Loucks-Horsley, S., Hewson, P., Love, N. and Stiles, K. (1998). Designing professional development for teachers of science and mathematics. Thousand Oaks, CA: Corwin Press.