Most policies seeking to improve high school achievement historically either provided incentives for educators or punished students. Since 1991, however, over a dozen states, comprising approximately a quarter of the nation's high school seniors, have implemented broad-based merit scholarship programs that reward students for their high school achievement with college financial aid. This paper analyzes one of these initiatives, the Tennessee Education Lottery Scholarships, using individual-level data from the ACT exams. The program did not achieve one of its stated goals, inducing more students to prefer to stay in Tennessee for college, but it did induce large increases in performance on the ACT. Policies that reward students for performance do affect behavior and may be an effective way to improve high school achievement. (Contains 7 tables, 3 figures and 14 footnotes.)