margins that in some cases were larger than two standard deviations.
The second program, ThinkerTools, also emphasizes physics as modeling and features both computer simulations and inquiry with physical materials. The curriculum (White, 1993; White and Frederiksen, 1998) teaches the physics of force and motion and is designed to be successful with students in middle school and in urban environments as well as in high school and in suburban environments.
The inquiry-based curriculum engages students’ preconceptions by asking them what they think will happen when certain forces are applied to objects. Students test their ideas in a computer-simulated world and learn when their ideas hold true and when not. The observations allow students to directly challenge their ideas and to engage in a search for a theory that can adequately explain what they observe. The class functions as a research community, and students propose competing theories. They test their theories by working in groups to design and carry out experiments using both computer models and realworld materials. Finally, students come together to compare their findings and to try to reach consensus about the laws and causal models that best account for their observations.
Students systematically build conceptual understanding by encountering problems that increase in complexity and difficulty. The problems are based on knowledge about typical forms of student thinking and its progression. Experiences that students encounter support the “conditionalized” kind of knowledge that experts hold, allowing students to detect patterns that novices do not see. ThinkerTools provides multiple experiences with problem solving, but the carefully controlled difficulty of problems is designed to build pattern recognition efficiently.
Like the modeling method, the emphasis is on constructing and revising models and explanations, and modeling ability is acquired in the service of building a conceptual understanding of motion, gravity, friction, and the like. What is distinctive in the ThinkerTools curriculum is the addition of a “reflective assessment” component. In addition to engaging in inquiry learning, students learn to evaluate the quality of their own and others’ inquiry investigations using standards that reflect the culture and the goals of the scientific community.
As with the modeling method, student achievement gains with the ThinkerTools curriculum are impressive. Students con-