We propose a theory of education curricula as horizontally differentiated by their paces. The pace of a curriculum and the preparedness of a student jointly determine the match quality of the curriculum for this student, so different students derive different benefits from learning under the same curriculum. Furthermore, a change in the curricular pace has distributional effects across students, benefiting some while hurting others. We test the model prediction using a quasi-natural experiment we call the G8 reform in Germany, which introduced a faster-paced curriculum for academic-track students. We find evidence consistent with our theory: While the reform improves students' test scores on average, such benefits are more pronounced for well-prepared students. In contrast, less-prepared students do not seem to benefit from the reform.