The rise in college preparatory coursework across American high schools appears not to affect college enrollment and graduation rates. This study uses the Civil Rights Data Collection to evaluate three stages along the college preparatory pipeline: access to, enrollment in, and mastery of Advanced Placement® and International Baccalaureate® coursework to understand the cumulative academic opportunities shaping students' college readiness. Leaks in the pipeline divert out historically marginalized students. An adaptation of the Herfindahl-Hirschman Index captures the magnitude of these racial and ethnic disparities. Social context explains where school and district resources alleviate disparities to provide more equitable (i.e., proportionally representative) academic opportunities. These findings offer substantive direction to improve equality in students' college readiness opportunities.