This report summarizes short-term impacts of the Quantum Opportunity Program (QOP) demonstration, which helped at-risk high school-age youth graduate and enroll in postsecondary education or training. QOP involved intensive case management and mentoring emphasizing after school supplemental academic education, developmental activities, and community service. It served a single cohort of youth from ninth grade in 1995 through fall 2000. A local community based organization in each of six inner city communities and one rural community teamed with a school to implement and operate a QOP program. The study examined how well the program was implemented at each site, how much it cost, how much time enrollees spent on program activities, and how QOP affected enrollees in the short term. Data from site visits, QOP conferences, conference calls with QOP staff, and student surveys indicated that QOP achieved short-term success in raising high school completion rates and enrollment in postsecondary education or other training. It did not improve grades and achievement test scores or reduce risky behaviors. QOP benefited enrollees in the middle of the eligible grade distribution more than enrollees at the top or bottom. Most enrollees attended very few program activities. Impact varied by site. Impacts for the whole QOP demonstration were substantially attributable to the impacts of two sites. (SM)