ABSTRACT This study used an ecological approach to studying adolescent mathematics ability development by classifying their mathematics ability growth trajectories and examining contextual measures differentiating the identified classes. Longitudinal student and parent data were collected for Taiwanese students in Grades 7, 9, 11, and 12 (n = 4,163). Growth mixture modelling identified 4 growth classes: low-increase, middle-flat, middle-increase, and high-increase. Multivariate analysis of variance revealed that girls’ mathematics ability improved and that boys started as middle or high mathematics achievers. Moreover, mathematics ability related to socioeconomic status and academic programmes, persistent parental monitoring related to desirable ability development, and student-perceived teaching quality related to student ability. High-increase students reduced their engagement in leisure activities when preparing for examinations, but they felt little mathematics frustration, whereas the opposite was true for low-increase students.