Ethnic-racial socialization is one strategy Black parents use to support their children's school engagement and academic achievement given the occurrence and toxic effects of discrimination. Egalitarianism and preparation for bias socialization messages have yielded mixed evidence of promotive and protective effects for Black youth's school outcomes, and effects may vary according to ethnicity. Thus, this research examined associations between ethnic-racial socialization messages and school engagement and achievement, and whether these messages protected against teacher discrimination effects on academic achievement transmitted through school engagement, among a nationally representative sample of Black adolescents who participated in the National Survey of American Life Adolescent supplement study. Ethnic-racial socialization message content and the frequency of communication about race demonstrated different associations with engagement (i.e., school bonding, aspiration-expectation discrepancy, and disciplinary actions) and achievement (i.e., grades) for African American and Caribbean Black youth. However, the benefits were not sufficient to combat the adverse effects of teacher discrimination on school engagement and, in turn, achievement. These findings highlight the utility of integrating ethnic-racial socialization into prevention programs to support Black youth's school experiences; demonstrate the importance of attention to heterogeneity within Black youth; and underscore the critical need for prevention programs to address teacher discrimination.