Stereotype threat has been shown to have deleterious impacts on the short- and long-term academic performance and psychological well-being of racial and ethnic minority students. Psychological variables related to this identity threat represent significant sources of achievement and attainment gaps relative to nonstereotyped Asian and white students who do not tend to be subject to performance declines related to such threats. In the current study, we investigate long-term effects of a brief self-affirmation intervention implemented at-scale to mitigate stereotype threat for seventh-grade African American and Latino students. Relative to their control-group counterparts, our findings indicate that a self-affirming intervention to buffer racial and ethnic minority students from identity threats reduced the growing achievement gap by 50% per year between seventh and 12th grade (N = 802). As a result, the achievement gap between white/Asian and African American/Latino students decreased by 42% at the end of 12th grade. Finally, the intervention increased on-time graduation rates for treated minority students by 10 percentage points (N = 952). Implications for theory, policy, and future research are discussed.