In this study, we investigate the growth trajectory of 519 students in a vocational senior high school in Taiwan. The group-based trajectory model identifies 3 subgroups with distinct trajectories of academic achievement in Math and English. This study reveals baseline predictive factors associated with these trajectories as well as relationships between different trajectories and students' college entrance examination scores. Our analysis contributes to the literature in two ways. First, this study shows that when school practices focus on improving the performance of students in the low achievement group, the performance of those in the middle is sacrificed. Second, upon their enrollment, students in the low achievement group appear to have significantly lower academic preparation and educational aspirations.