The committee also identified seven crosscutting ideas, which are similar to those articulated in other standards:
• cause and effect: mechanism and explanation;
• scale, proportion, and quantity;
• systems and system models;
• energy and matter: flows, cycles, and conservation;
• structure and function; and
• stability and change.
Some of these ideas may go by different names in different contexts, Reiser stressed, but they apply across disciplines. For example, he explained, whether one is exploring phenomena in biology or earth and space sciences, a good strategy is to figure out where energy is going and how it is changing form: “Once you realize that you can’t create or destroy any of it for free, that is, a really powerful heuristic that you can use across all different kinds of scientific problems.” Several of these ideas are particularly valuable in explaining and reasoning about climate change, he added.
A second way the framework is important, Reiser explained, is in its commitment to the idea that learning develops over time. This is not a controversial idea, he noted, but “unfortunately this is not the way our science education system is broadly implemented.” In his view, current approaches typically take necessary prerequisites into account but do not focus on carefully building understanding over time. For students to learn complex explanatory ideas they must revisit core ideas in new contexts that force them to extend their understanding, and engage in tasks that force them to synthesize and apply ideas. Reiser pointed out that there is a deliberate commitment in the new framework to the articulation of “a story line about how ideas develop over time.” Figure 3-1 illustrates the progression of one of the core ideas, the structure of matter.
A third way the framework is important, in Reiser’s view, is in its recognition that teaching content is necessary but not sufficient. Prior standards have also focused on inquiry, he noted, but the new framework better articulates what it means and how to teach it. “We can’t teach scientific ideas without engaging students in practice that involves making sense of the ideas, applying them, extending them, explaining data—even using arguments from evidence to evaluate the consequences of different possible decisions,” he explained. Thus, the framework calls on standards developers to create performance expectations that integrate all of these elements. Standards based on this approach would not yield “chapter one on the scientific method,” he observed. “You can’t teach the scientific