Educators and policy makers have placed leadership development at the top of the school reform agenda, believing that aspiring and new school leaders can learn the necessary skills to improve the most challenging schools. Leadership development builds the capacity of educators (teachers and administrators) to be effective in leadership roles or processes, enabling leaders to work together in productive and meaningful ways that benefit student learning. School leaders need to know how to effect the changes necessary to "move the needle" on school performance. To be effective requires developing skills in various arenas, including leading change, focusing interventions, managing resources, improving instruction, and analyzing results. This type of professional learning must develop an individual's skill set within the context of teaching and learning in a particular school or district. In this article, the authors first discuss three key drivers of leadership development: (1) assessment; (2) challenge; and (3) support. They then identify conditions that contribute to the success of leadership development initiatives. Finally, they discuss the insights that research provides for school district leaders to support leadership development.