The significant expansion of student testing, while controversial in many countries, has not been generally linked to educational performance. We investigate how different testing regimes – which provide varying information to parents, teachers, and decision makers – relate to student achievement. Our empirical analysis exploits data from over two million students in 59 countries observed across six waves of the international PISA test 2000-2015. Relying on the country panel feature of the data, we investigate how testing reforms relate to country performance on PISA tests over time, taking out country and year fixed effects. In low- and medium-performing countries, expansion of standardized testing is associated with improvements in student achievement, whereas reforms relating to internal reporting and teacher monitoring are not. By contrast, in very high-performing countries expansion of standardized internal testing and teacher monitoring may actually harm achievement.