Data from 3 waves of the Children of Immigrants’ Longitudinal Survey in 4 European countries (CILS4EU) were used to test for effects of academic trajectories on the development of ethnic retention. The large-scale comparative panel data for the transition at the end of lower secondary school provide answers to the following research questions: Is migrant youth with unmet educational aspirations especially vulnerable to ethnic retention? Is ethnic retention after failure of the academic career enhanced or buffered by societal conditions, i.e., does it vary with educational and social welfare systems? Ethnic retention was captured in 4 dimensions: social retention (ethnic friends), cultural retention (ethnic language use), religious retention (ethnic religiosity), and emotional retention (ethnic identification). Fixed-effects regressions with interaction terms tested the effects of academic track and aspirations in combination with reactive ethnicity and are tested separately for each country. As compared to Sweden, migrant minority youth in England and Germany are much more likely to develop ethnic emotions and practice a minority religion. However, in the fixed-effects analysis capturing within-individual changes, youth with increased educational aspirations but unfavorable career development did not differ substantially from the other career patterns, and if so, they showed lower levels of ethnic retention.