In the last decade, five U.S. states adopted mandates requiring high school juniors to take a college entrance exam. In the two earliest-adopting states, nearly half of all students were induced into testing, and 40-45% of them earned scores high enough to qualify for selective schools. Selective college enrollment rose by 20% following implementation of the mandates, with no effect on overall attendance. I conclude that a large number of high-ability students appear to dramatically underestimate their candidacy for selective colleges. Policies aimed at reducing this information shortage are likely to increase human capital investment for a substantial number of students.