This ethnographic and historical study of science curriculum, policy, and their relationship describes and analyzes the science that schools actually teach, and how, in what circumstances, and with what private and public consequences diverse constituents in and around public schools struggle to define it. It takes as its specific case, "integrated science," a key component in state and national systemic reforms aimed at redefining the traditional "layer-cake curriculum." The locus for the research is two comprehensive high schools in one of southern California's largest school districts, and the policy arena in the state. The study will provide a comprehensive model of school science, its politics, and its place in the broader scientific culture that defines modern American culture. By providing readers the concrete and conceptual resources to understand school science in the research sites and to recognize comparable findings in other studies and schools that they know, the project is designed to foster public deliberation about high school science.