This study showed that working during high school had negative effects on 15 of 23 Grade 12 and postsecondary outcomes such as achievement, coursework selection, educational and occupational aspirations, and college attendance. These effects were found with control for background variables and parallel outcomes from Grades 8 and 10 based on the 8-year (four-wave), nationally representative National Education Longitudinal Survey of 1988. The only benefit of working was a reduction in postsecondary unemployment, but even this effect was nonlinear. In the case of most outcomes, the effects of hours worked were primarily linear and negative and were consistent across ethnicity, gender, socioeconomic status, initial ability levels, and different types of work. Among continuing students who worked during high school, however, working to save money for college had mostly favorable effects. (Contains 1 note, 6 tables and 1 figure.)