School principals have complex jobs. To better understand the work lives of principals, this study uses observational time use data for all high school principals in one district. This article examines the relationship between the time principals spent on different types of activities and school outcomes, including student achievement, teacher and parent assessments of the school, and teacher satisfaction. We find that time spent on organization management activities is associated with positive school outcomes, whereas day-to-day instruction activities are marginally or not at all related to improvements in student performance and often have a negative relationship with teacher and parent assessments.