In spring 2025, the authors surveyed 207 American School District Panel member districts about principal pipelines, preparations, and supports. In this report, the authors describe the principal pipeline in school districts across the United States and the prevalence of professional development (PD) targeted at building and strengthening high-quality school leaders within individual districts. These findings can inform state policymakers who are grappling with school leadership shortages by describing (1) where districts tend to find principals and (2) how that process varies by district characteristics and the types of PD that are most prevalent and for whom, including which PD opportunities districts should invest in for the future. These findings may also help universities that are redesigning pre-service leadership training programs by identifying gaps in leadership training offered by school districts.