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 Miami-Dade County Public Schools. This paper 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. The authors find that time spent on Organization Management activities is associated with positive school outcomes, such as student test score gains and positive teacher and parent assessments of the instructional climate, 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. This paper suggests that a single-minded focus on principals as instructional leaders operationalized through direct contact with teachers may be detrimental if it forsakes the important role of principals as organizational leaders. Percent of Principal Time Spent on Individual Tasks is appended. (Contains 6 footnotes, 3 figures and 5 tables.) [This paper was supported by the Stanford University K-12 Initiative.]