At the other end, learning progressions are anchored by societal expectations (values) about what society wants middle school students to understand about science. They are also constrained by research-based conceptual and social analyses of the structure of the disciplinary knowledge and practice that is to be learned. Analysis of disciplinary knowledge is important in helping to identify the core ideas in science—those of greatest explanatory power and scope—that it may be most important to teach, because they provide central frameworks for further learning. Examples of such core ideas are the atomic-molecular theory of matter and evolutionary theories of life’s diversity. In addition, analysis of disciplinary knowledge helps identify the network of ideas and practices on which those core ideas rest, and hence what will be important component ideas to develop as part of their construction.
Learning progressions propose the intermediate understandings between these anchor points that are reasonably coherent networks of ideas and practices and that contribute to building a more mature understanding. It is important to note that some of the important precursor ideas may not look like the later ideas, yet they crucially contribute to their construction. For example, realizing that objects are composed of materials and have some properties because they are made of that material is a critical first step toward understanding atomic-molecular theory. By thinking hard about what initial understandings need to be drawn on in developing new understandings, learning progressions highlight important precursor understandings that might otherwise be overlooked by teachers and educators.
The intellectual exercise of constructing learning progressions requires one to synthesize results from disparate (often short-term) studies in ways that begin to address questions of how longer term learning may occur; learning progressions suggest priorities for future research, including the need for engaging in longer term studies based on best bets suggested by these research syntheses; and they present research results in ways that make their implications for policy and practice apparent. Ultimately, well-tested ideas about learning progressions could provide much needed guidance for both the design of instructional sequences and large-scale and classroom-based assessments.
The learning progression approach has four characteristics that are mostly absent from accounts of domain-general developmental sequences and current standards documents.