Researchers have used many angles and perspectives to investigate how principals enact instructional leadership in schools. Most research has emphasized the practices of school leaders, although investigations of leadership styles and leadership processes are also present in the literature. In this study, the authors take a different approach by examining the scope of principal efforts to improve instruction. "Scope of principal effort" refers to the extent to which principals target or distribute their instructionally oriented work with teachers. Using data from principal web logs and teacher surveys conducted in 51 schools in an urban southeastern district, the authors develop models to examine not only differences in average instructional change at the school level but also variability in instructional change across teachers within schools. The results indicate that the scope of principals' instructional leadership activities varies from one school to the next, from very broad approaches that target the entire faculty to very targeted approaches that focus on a few teachers, and that the frequency of a principal's instructional leadership activities with an individual teacher is directly related to the magnitude of instructional changes reported by that teacher. These findings support the notion that principals who focus on the improvement of particular teachers in conjunction with broader approaches can produce greater changes in instructional practice. (Contains 1 note, 3 tables, and 2 figures.)