Taking advanced courses in high school predicts many positive outcomes, yet low-income students and students who identify as Black and Hispanic are underrepresented. Policies such as "algebra for all" that accelerate middle school students into advanced courses are well-studied, but little is known about newer academic acceleration policies that target older students. Between 2014-2015 and 2016-2017, 72 districts in Washington implemented Academic Acceleration policies, which identified proficient 11th- and 12th-grade students for automatic acceleration into AP, IB, and other dual credit courses. We used difference-in-differences models to examine changes in advanced course enrollments, GPAs, and high school graduation between districts that began implementing the policy at different times. We found advanced course enrollment increased and became more equitable postpolicy.