We test the hypothesis that the abolition of school performance tables negatively affects school effectiveness. Our data allow us to implement a classic difference-in-difference analysis comparing outcomes in England and Wales, before and after the abolition of the tables in Wales. We find significant and robust evidence that this reform markedly reduced school effectiveness in Wales relative to England. There is significant heterogeneity across schools: schools in the top quartile of the league tables show no effect. We also report that the reform had no systematic significant impact on either sorting by ability or by socioeconomic status.