grow, and about temperature and weather. Like the high school physics students described in the preceding section, children are sense-makers, and their theories and ideas are tools that should be encouraged and stretched, not ignored. As children accumulate greater experience with the world, they begin to master the kinds of distinctions that adults and scientists make: dogs are indeed alive and rocks are not, but plants are also alive, even though they do not move from place to place of their own volition.
Early conceptions may evolve somewhat with increased experience. But scientific conceptions generally do not develop without explicit instruction, partly because the epistemological assumptions that underlie them are complex and often invisible. As discussed with regard to physics, many important scientific processes, principles, and laws are at odds with everyday understandings and experiences. Much scientific work requires methods and measurements that are not characteristic of everyday activity, and that rely on instruments that allow the scientist to explore what is not otherwise accessible.
Even more fundamentally, it is by no means self-evident to children what kind of enterprise science is. Experimentation, for example, requires arranging aspects of the world to generate a model of the phenomenon that is of interest. The model, which is taken to stand for the more general class of events, is then systematically perturbed as a way to seek deeper understanding. The history of science suggests that this way of constructing knowledge evolved gradually, as practicing scientists increasingly came to regard their work as the creation of a form of argument, rather than as the unproblematic observation of transparent events in the world (e.g., Bazerman, 1988).
While a scientific approach is not likely to develop in children naturally, this form of thinking can be developed gradually when students have sustained opportunities (as in Sister Hennessey’s classroom, described below) to learn the discipline’s content knowledge (what we know), theory (what we make of what we know and don’t know), and knowledge of the epistemologies of science (how we know). But little is known about the routes or the progression of understanding that characterize effective mastery of science content and reasoning.
What science are children capable of learning at different grade levels? Elementary school children studying marine mammals may be quite capable of understanding that the ancestors