Educators in public schools in the United States are typically enrolled in defined-benefit pension plans, which penalize across-plan mobility. We use administrative data from Missouri to examine how the mobility penalties affect the labor market for school leaders, and show that pension borders greatly reduce leadership flows across schools. Our most conservative estimates indicate that removing a pension border that divides two groups of schools will increase leadership flows between the groups by roughly 100 percent. We consider the implications of our findings for workforce quality in schools near pension borders in Missouri. Our results are of general interest given that thousands of public schools operate near pension boundaries nationwide. Appended are: (1) Details for the Pension-Wealth Calculations; (2) Procedure for Determining the Effective Number of Simulations; and (3) Supplementary Tables. (Contains 6 figures, 12 tables and 45 footnotes.)