Many have called for improved alignment between high school graduation and college admission requirements. However, few have empirically examined the extent to which courses needed for college admission are not offered by high schools, which I call underalignment. Using high school-level data from the Office for Civil Rights, I examined high school math underalignment relative to public flagships' published minimum math requirements. Overall, 2.2% of public high schools did not offer the math course required for admission by their respective state flagship. Because minimum requirements may not reflect competitive admission processes such as those found at selective flagships or for intended science, technology, engineering, and mathematics (STEM) majors, I estimated 2 additional benchmarks: the probable math requirement based on the flagship's selectivity and the highest math course most commonly taken by entering STEM majors. When considering probable and STEM math benchmarks, underalignment was higher--6.9% and 29.0% of high schools, respectively. Findings from logistic regression analysis show low-income student-of-color high schools have a higher probability of underalignment compared with most other high school types, net of school characteristics and state-level fixed effects across all three benchmarks. Policy implications for improving alignment and equity are discussed.