Schools that support teachers and other members of the school community in taking initiative and exercising leadership over their work look and feel different from schools where decision-making and influence are more centralized. A growing body of research, backed by the experience of teachers and school leaders across the country, supports the notion that expanding leadership--or "distributing leadership"--is a critical strategy for addressing the professional needs of educators, catalyzing existing and nascent leadership within a school community, and achieving real, sustained results for students. To help policymakers at all levels more deeply understand distributed leadership and the variety of ways it may manifest at the school level, we conducted a comprehensive review of the research on distributed leadership. Our goal is to support policymakers in developing evidence-based strategies to support distributed leadership and improve school and student outcomes. Our findings and recommendations are summarized in the Policy Primer. For those who want to dig deeper into the research, we offer an explanation of our definition (Resource A), more detail on our findings from the literature review along with relevant citations (Resource B), and reflections on how research limitations should inform policy decisions (Resource C). Finally, to bring the research and policy actions to life, we have developed a series of vignettes that show how school and system leaders are distributing leadership and, together, improving results for schools and students. By capturing their learning and experiences, we aim to help illustrate what is possible when supportive, evidence-based practices and conditions are in place.