cal and life sciences) and has implications for developing an informed citizenry able to understand current practical issues and policy debates (environmental issues and problems). Currently, other design teams are working on learning progressions for other core ideas (genetics, matter cycling). We think more work on describing such large-scale learning progressions is going to be crucially important to the improvement of science education in the United States.


As mentioned above, research on children’s learning is currently fragmentary, falling well short of suggesting a complete sequence of steps in learning about matter or any other topic. We therefore need to make principled use of the research to suggest the general nature of a learning progression that would lead to understanding and to fill in the gaps when research is not available. In developing a learning progression for the atomic-molecular theory of matter, we suggest reasonable steps that are constrained by three of the four strands of scientific proficiency: (a) students’ existing concepts, (b) their knowledge construction and evaluation abilities, and (c) their understandings of science as a way of knowing. (Research focusing on the fourth strand, productive participation in science, currently is not easily integrated with research focusing on the first three within a learning progression focused on matter.)

Thus, in describing the learning progression, we discuss how it reflects the interactions among these three kinds of constraints and how competence in the first three strands of scientific proficiency can develop interactively. We also discuss some of the research base for the steps in the progression, the way it challenges some aspects of existing practice and provides guidance for ways of elaborating the science standards, as well as important limitations in the existing progression and questions raised for future work.

Grades K-2
Developing an Understanding of Materials and Measurement

The learning progression developed by Smith et al. (2004) identifies several ideas (concepts, resources, abilities) that children have at the start of elementary school that enable them to begin their initial exploration of three basic questions. The learning progression is described in part as the progressively more sophisticated answers that children can give to these questions (the overview table in Appendix A describes the learning progression in these terms):

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