Use of the current research base: We suggest that learning progressions should make systematic use of current research on children’s learning (reviewed in Part II) to suggest how well-grounded conceptual understanding can develop. For more on how the research can be used, see the example developed below.
Interconnected strands of scientific proficiency: Learning progressions consider the interaction among the strands of scientific proficiency in building understanding (know, use, and interpret scientific explanations of the natural world; generate and evaluate scientific evidence and explanations; understand the nature and development of scientific knowledge; participate productively in scientific practices and discourse) and always involve students with meaningful questions and investigations of the natural world.
Organization of conceptual knowledge around core ideas: Learning progressions recognize that the first strand of scientific proficiency (understanding and using scientific explanations) involves far more than learning lists of facts. Scientific understanding is organized around conceptual frameworks and models that have broad explanatory power. The purpose of concepts is to extend understanding—to allow one to predict, understand, and explain phenomena one experiences in the world—as well as to solve important problems. It is therefore important to explicitly recognize these frameworks and to help children develop them through instruction that involves model building and conceptual change.
Recognizing multiple sequences and web-like growth: Learning progressions recognize that all students will follow not one general sequence, but multiple (often interacting) sequences around important disciplinary-specific core ideas (e.g., atomic-molecular theory, evolutionary theory, cell theory, force and motion). The challenge is to document and describe paths that work as well as to investigate possible trade-offs in choosing different paths.
In the development of learning progressions that are research-based and reflect the variety of ways that children can learn meaningfully about a topic, there are three challenges, none of which can be completely overcome with the existing research base: (1) describing a student’s knowledge and practice at a given point in the learning progression, (2) describing a succession of ways students can understand a topic that show connections between ways and respect constraints on their learning abilities, and (3) describing the variety of possibilities for meaningful learning for students with different personal and cultural resources or different instructional histories. We discuss each of these challenges below.