In recent decades, much attention has been focused on student achievement in the United States. Many policy initiatives have been attempted in an effort to bolster achievement, including increasing school revenue, decreasing class size, expanding early childhood programs, and introducing vouchers and charter schools, to name a few, but not all of these initiatives have had the desired impact. Research has shown that other, less tangible factors such as teacher quality and the characteristics of a student's peers may play a much greater role. This research focuses on one of these less tangible factors: principal quality. This paper has two main goals. The first is to measure principal quality by estimating principal value added to student achievement. The authors estimate a set of principal fixed effects from test score gains with data on North Carolina students between third and eighth grade. The second goal is use the estimated principal value added to determine what makes a principal better than another at raising test score value added. (Contains 1 footnote.)