After more than three decades of development and two decades of evaluation, career academies have been found to be effective in improving the performance of students in high school, particularly for students at greatest risk. Career academies have become the most durable and best-tested component of a high school reform strategy that includes dividing large schools into smaller units. The number of career academies has been expanding rapidly because they have been found to be effective and because they embody ideas promoted by several major high school reform movements, including school-to-work advocates, the Coalition of Essential Schools, and the small schools movement. Today most career academies combine a college prep curriculum with a career-related theme and occupational training partnerships with employers. Most of their students attend four-year colleges. (Six tables list the findings of various studies of career academy growth; performance of career academy students and graduates; academic performance and high school completion of students in career academies compared to other students; postsecondary education enrollment of career academy graduates; employment rates after high school of students in career academies compared to other students; and effects of dividing large high schools into smaller subunits. A list of 65 references is included.) (KC)