School districts occupy center stage in education reform in the U.S. They manage nearly all public funding and are frequently the locus of federal and state reform initiatives, e.g., instituting meaningful teacher evaluation systems. Financial compensation for district leaders is high, with many being paid more than the chief state school officers who oversee the entire systems in which they serve. Despite the centrality of school districts in all the ways described, one knows very little from existing research about how important they are to student achievement relative to other institutional components for delivering education services, including teachers and schools. Neither does one have information on the size of the differences in effectiveness among districts or whether there are districts that show exceptional patterns of performance across time, e.g., moving from low to high performing. The authors begin to fill these information gaps in the present report by analyzing 10 years of data involving all public school students and school districts in Florida and North Carolina. They find that school districts account for only a small portion (1% to 2%) of the total variation in student achievement relative to the contribution of schools, teachers, demographic characteristics of students, and remaining individual differences among students. There are also districts that have displayed exceptional patterns of performance in terms of student achievement over the last decade, including districts that beat their demographic odds every year, districts that consistently underperformed, districts that had nose-dive declines, and districts that experienced transformative growth. These findings provide an empirical justification for efforts to improve student achievement through district-level reforms and should be a tantalizing fruit for those who want to better understand why some districts are better than others and translate that knowledge into action. (Contains 6 figures and 7 endnotes.)