In Systems for Instructional Improvement, Paul Cobb and his colleagues draw on their extensive research to propose a series of specific, empirically grounded recommendations that together constitute a theory of action for advancing instruction at scale. The authors outline the elements of a coherent instructional system; describe productive practices for school leaders in supporting teachers’ growth; and discuss the role of district leaders in developing school-level capacity for instructional improvement. Based on the findings of an eight-year research-practice partnership with four large urban districts investigating their efforts to enhance middle school math instruction, the authors seek to bridge the gap between the literature on improving teaching and learning and the literature on policy and leadership. They look at the entire education system and make recommendations on improvement efforts with a focus on student learning and teachers’ instructional vision. In particular, the authors offer insights on the interplay among various supports for teacher learning, including pullout professional development, coaching, collaborative inquiry, the most instructionally productive uses of principals’ time, and the tensions that tend to emerge at the district level. They provide a guide for district-level leaders in organizing their work to support significant teacher learning. Systems for Instructional Improvement provides an invaluable resource for school and district leaders, while outlining a clearly focused agenda for future research.