This paper studies the effects of guaranteed college admission on student effort and achievement. In 1997, Texas enacted the "Top Ten Percent" law, which guarantees admission to any public college for students in the top ten percent of their high school class. In practice, eligible students become aware of their admission status at the end of their junior year in high school--more than 1 year prior to attending college. We use data from a large, urban school district and regression discontinuity methods to test for effects on effort. Our preferred estimates show that students who barely qualify for the admissions guarantee earn marginally lower grades and take fewer advanced courses in their senior year compared to students who do not qualify for guaranteed admission and learn their status in the final senior year term. We find qualitatively similar results when limiting our sample to finer bandwidths, although the estimates are imprecise.