Over the past several years, education reformers have increasingly invested in the development of communities within schools as a central strategy to improve teaching and student learning. These communities come in various guises, including small schools, small learning communities, and teacher teams. Two assumptions about how these communities will enhance the quality of instruction underlie the push for these more intimate learning environments. First, supporters believe that teachers will get to know their students better and therefore be more able to respond to students’ learning needs. Second, advocates contend that small communities will encourage teachers to collaborate more in order to improve their instructional practices. Thus, the theory of action underlying the development of teacher communities is that the fostering of these kinds of teacher communities will instigate improvements in the quality of instruction, which will lead to enhanced student learning. This issue of CPRE Policy Briefs examines the merit of these assumptions and the conditions under which communities of teachers can improve their instructional practices and bring about enhanced student learning. The lessons for policymakers contained in this Brief come from large-scale evaluations of two major district reform initiatives — one in Philadelphia, Pennsylvania and the other in Cincinnati, Ohio — that were designed to foster the development of instructionally focused communities. The research from these two very different settings indicates that only under certain conditions will teacher communities flourish into communiDeveloping Communities of Instructional Practice: Lessons from Cincinnati and Philadelphia By Jonathan A. Supovitz and Jolley Bruce Christman ties engaged in instructional improvement. The findings suggest that in order for an investment in communities to pay off in widespread improvement in student learning, particular kinds of teacher communities are needed: those that are focused on improving the instructional core of schooling and provided with the necessary strategies, structures, and supports. With more specific guidance that helps teachers to hone their instructional craft knowledge, policymakers can foster communities of instructional practice.