Focusing on the school principal's day-to-day work, we examine who leads curriculum and instruction- and administration-related activities when the school principal is not leading but participating in the activity. We also explore the prevalence of coperformance of management and leadership activities in the school principal's workday. Looking across a range of administration-related and curriculum and instruction-related activities school principals participate in, we show that who takes responsibility for leading and managing the schoolhouse varies considerably from activity to activity and from one school to the next. (Contains 6 tables, 1 figure and 2 footnotes.)