This paper makes the case for a shift in the policy strategy to improve K-12 education. It argues for investment in an infrastructure to develop the knowledge base on effective teaching and learning, and to prepare new teachers according to that knowledge base. As in medicine, the infrastructure would be located within practice settings, and consist of a set of schools within school districts that serve as the sites for research and development focused on practice, and for the induction of new teachers. The corridor of schools stretching from the earliest grade through graduation would be a critical point of intersection for faculty from research and teacher preparation institutions, and K-12 teachers and administrators.