Relatively few studies have successfully linked specific features of principal learning—in either preservice preparation or in-service professional development—to teacher and student outcomes. Further, most studies of principal professional learning have examined the efficacy of particular programs rather than the mix of program features and experiences to which principals have had access. To begin to address this gap in the literature, this study from the Learning Policy Institute examined the relationship between principal learning opportunities (both preservice preparation and in-service professional development) and key outcomes for the teachers and students in their schools. The authors examined both teacher retention and student achievement gains in English language arts and mathematics. This study offers a new perspective on the efficacy of professional learning by using detailed data from a large, representative sample of principals directly linked to individual-level information from the teachers and students in their schools.