Continuing efforts have been made in the United States (US) to examine the role of schooling in alleviating the ethnic/racial inequalities in student performance. Using the US data from the 2012 Programme for International Student Assessment (PISA), this study examines the between-school and within-school racial/ethnic differences in opportunities to learn (OTL) and their relationship to the corresponding differences in student mathematics achievement. In all models and for all types of students, OTL showed a significantly positive relationship to student mathematics achievement, and its effect size was about four times as large as the socioeconomic status (SES) effect. The results suggest the importance of OTL in alleviating the racial/ethnic inequalities in mathematics performance.