This article examines the relationship between school district size and the educational performance of its students. Measures of student performance such as standardized test scores and pass rates, End of Course Assessment (ECA) pass rates and Advanced Placement (AP) pass rates are used. Using Indiana school district data, we nd that school district size plays a signicant role in student performance. Increasing the size of small school districts to around 1,000 students would increase the average student's performance on the SAT by 48 points; biology ECA pass rates by 10 percentage points and ISTEP eighth grade pass rates by 8 percentage points. Increasing the size of school districts to 2,000 students would further increase SAT scores in addition to increasing ACT scores by 0.85 points and pass rates on AP exams by 14.5 percentage points. Student performance on the algebra End of Course Assessment (ECA) and the share of students earning honors diplomas improves in school districts approaching an enrollment level of 4,000 students. Increasing school district size had no statistically signicant impact on End of Course Assessments in English.