This brief from the Learning Policy Institute summarizes research on the important role that school leaders can play in reducing the steady churn of teachers that can worsen shortages and undermine students’ educational opportunities. Principal leadership plays a significant role in teacher turnover. Teachers identify the quality of administrative support as a key factor in decisions to leave a school. In addition, teachers point to the importance of school culture and collegial relationships, time for collaboration, and decision-making input—also areas in which the principal plays a central role. Principals tend to be weaker in high-poverty, low-achieving schools, where principal quality can have an even greater bearing on teacher attrition. Local, state, and federal policymakers have a role to play in recruiting and training principals. It concludes with a discussion of how local, state, and federal policymakers can strengthen the preparation and ongoing development of principals to create learning environments that better enable students and teachers alike to thrive. The passage of ESSA provides one such opportunity, as local and state policymakers can leverage federal ESSA funding to strengthen principal preparation and development.