Accounting for a quarter of a school's impact on student achievement, principals are the leverage point for education reform and the primary drivers of school improvement. School leaders have a greater influence on all students than teachers and are the best long-term investment in effective teaching at scale. Like all professionals, teachers, assistant principals, and principals want opportunities to grow over the course of their careers. Successful educators have job opportunities beyond the school, and many leave to pursue other careers within and outside the education sector. Many of the strategies to increase teacher retention are practices driven by principals--including providing feedback and development, offering recognition, and providing new responsibilities or advancement opportunities, such as staying in the classroom part-time while taking on additional leadership responsibilities. This brief suggests that developing a pipeline of future leaders through teacher leadership and assistant principal roles will help address a number of challenges at the local level. It gives potential future leaders hands-on practice with adult leadership. It creates career pathways for teachers to explore expanding their reach while remaining in the classroom. And it helps schools and Local Education Agencies (LEAs) plan for future leadership needs. Finally, principals can't do it alone. New Leaders has found that great principals in their highest-performing schools build leadership teams and delegate responsibilities in order to manage the school effectively, to engage teachers in decision-making, and to develop future school leaders. [For the full series, see "Prioritizing Leadership: New Leaders' Federal Policy Platform" (ED559351).]