This study examines the effectiveness of math and English transition courses with added supports through the At Home in College program in New York City, which was developed by the City University of New York. Taken together, the findings suggest that offering the program is likely neutral to mildly beneficial and at least not harmful to high school seniors. Yet because the counterfactual circumstance typically includes a college-preparatory course of some kind that is displaced in favor of the treatment, it is important for policymakers and educators implementing transition courses to carefully consider the unintended consequences of removing students from alternative courses.