Most German states have reformed university preparatory schooling during the last decade by reducing its duration from 13 to 12 years without changing the graduation requirements. In this paper, we use nationwide data on high school graduates and apply a difference-in-differences approach to evaluate the reform effects on post-secondary education decisions. The results show that enrollment in university education in the first year after high school graduation is reduced in all analyzed states, while participation in voluntary service or staying abroad is increased. In some subgroups, depending on state, gender and family background, university enrollment is decreased additionally beyond the first year.