This project is developing an approach to science education that enables sixth graders to learn principles underlying Newtonian mechanics, and to apply them in unfamiliar problem solving contexts. The students' learning is centered around problem solving and experimentation within a set of computer microworlds (i.e., interactive simulations). The objective is for students to gradually acquire an increasingly sophisticated causal model for reasoning about how forces affect the motion of objects. To facilitate the evolution of such a mental model, the microworlds incorporate a variety of linked alternative representations for force and motion, and a set of gamelike problem solving activities designed to focus the students' inductive learning processes. As part of the pedagogical approach, students formalize what they learn into a set of laws, and critically examine these laws, using criteria such as correctness, generality, and parsimony. They then go on to apply their laws to a variety of real world problems. The idea is to synthesize the learning of the subject matter with learning about the nature of scientific knowledge — its form, its evolution, and its application.Instructional trials found that the curriculum is equally effective for male sand females, and for students of different ability levels. Further, sixth graders taught with this approach do better on classic force and motion problems than high school students taught using traditional methods.