Using national transcript data, the authors examine inequality in access to an advanced curriculum in high school and assess the consequences of curricular intensity on test scores and college entry. Inequalities in curricular intensity are primarily explained by student socioeconomic status effects that operate within schools rather than between schools. They find significant positive effects of taking a more intense curriculum on 12th-grade test scores and in probabilities of entry to and completion of college. However, the effect sizes of curricular intensity are generally modest, smaller than advocates of curricular upgrading policies have implied. (Contains 3 tables.)