The high school government course is arguably the main site of formal civic education in the country today. This article presents the curriculum that resulted from a multiyear study aimed at improving the course. The pedagogic model, called "Knowledge in Action," centers on a rigorous form of project-based learning where the projects are weeks-long simulations. The first section introduces the course and the study, the second describes the methodology and design principles, the third describes the political simulations that are the spine of the course, and the fourth examines implementation and design issues that emerged across the years. The latter are concerned with the centrality of simulations, the selection of core content and skills for deeper learning, and the ongoing struggle to help students learn from texts. Readers are invited to adopt or adapt any of the design elements to suit their needs.