The work principals do has always mattered, but as the demands of the job increase, it matters even more. Perhaps once they could maintain safety and order and call it a day, but no longer. Successful principals today must also lead instruction and nurture a productive learning community for students, teachers, and staff. They set the tone for the school's academic focus and ever-improving professional practice. This article describes how six school districts are taking up the challenge of ensuring their schools have a supply of effective principals, and their experiences can point other district and state leaders to how to do it. The six districts are: (1) Charlotte-Mecklenburg Schools, North Carolina; (2) Denver Public Schools, Colorado; (3) Gwinnett County Public Schools, Georgia; (4) Hillsborough County Public Schools, Florida; (5) New York City Department of Education, New York; and (6) Prince George's County Public Schools, Maryland.