Research has shown that academic self-concepts (ASCs) are subject to contextual influences, in particular to the big-fish-little-pond effect (BFLPE). The BFLPE refers to the phenomenon whereby able students report more negative ASC when exposed to learning environments with relatively higher-achieving students. Although the BFLPE has been identified across various educational settings, there is surprisingly little research on its persistence across contexts. The present study fills this gap and explores the lasting consequences of the BFLPE for ASC development after the transition from one educational context to another. It draws on a longitudinal study of N = 1,617 students from Grades 6 to 9, which followed students across the transition from elementary to secondary school. We found indications of cross-sectional BFLPEs in both elementary and secondary schools for all 3 of the ASC dimensions we investigated (general academic, German language arts, and mathematics). Yet, after students had transitioned into secondary schools, the effects of the elementary school context persisted to a certain extent, but this varied by self-concept domain: for general ASC (GASC), some elementary school effects remained during secondary schooling, alongside the new effect of the secondary school context. For German language arts and mathematics self-concepts, the BFLPE from elementary school faded after students transitioned from elementary school. BFLPEs varied by secondary school track for synchronous, cross-sectional effects but not for longitudinal elementary school effects.