Ensuring that every school has a strong leader is critical for student achievement. Estimating the impact of highly effective principals on student learning is challenging to pinpoint, but researchers agree that strong principals make a substantive and positive difference in student learning. Furthermore, the impact of a school leader is multiplied across the full school building -- usually reaching hundreds of students each year. This policy brief identifies two main focus areas for states working on supporting their principal pipelines and effectiveness of school leaders -- recruitment and professional development -- and offer strategies to improve school leader recruitment and retention.