In this study we to analyzed students’ mathematics achievement at the end of their final school year (Grade 13). Students came from traditional upper secondary schools (in German: Gymnasium; n = 1433) and from vocational upper secondary schools (in German: Berufliches Gymnasium; n = 2342). Previous research has shown that due to substantial achievement differences at the start of upper secondary school (Grade 11) students from traditional schools later outperform their peers at vocational schools. Mean differences at the end of upper secondary school often correspond to effect sizes of d > 0.50. In our study, however, substantial numbers of students at the vocational schools had more lessons per week (five vs. four at the traditional upper secondary schools) during the whole time of upper secondary school. This allowed us to test whether more learning opportunities in upper secondary school can level out achievement differences between both school types. Students worked on a mathematics test which covered contents of lower and upper secondary level. In line with our predictions no achievement differences occurred between the two groups. A third student group at vocational schools with only three lessons math per week, however, showed dramatically lower achievement levels. Based on our findings we argue for increasing learning opportunities in core subjects in vocational upper secondary schools.