The NGSS are based on the NRC Framework for Science
Education5 that is composed of three strands: disciplinary core
ideas, crosscutting concepts, and science (and engineering)
practices. Disciplinary core ideas (DCIs) are significant ideas of
broad importance to the discipline; they have explanatory
power, are generative of more specialized ideas, and can be
developed over time from K−12 (and beyond). The DCIs in
the framework are necessarily of a fairly large grain size. For
example, the first physical science core ideaPS-1, Matter and
its Interactionsis guided by the question “How can one
explain the structure, properties, and interactions of matter?”
The development of PS-1 begins in the early elementary years
with the idea that “matter exists as difference substances as
exhibited by their observable properties”5 and progresses
through high school where “the sub-atomic model and
interactions between electric charges can be used to explain
interactions of matter”.5 This research-based longitudinal and
developmental elaboration of a core concept is often termed a
learning progression.6