Students who eventually drop out of school have a long-term disadvantage in becoming productive citizens. The traditionally structured U.S. high school system does not facilitate high school education for at-risk students. Some schools, however, do organize themselves around the needs of the at-risk student population. This study analyzed the impact of a 6-month dropout prevention program in a nontraditional school of a large urban school district. Participants were students enrolled in the alternative high school program. A treatment and a comparison group were randomly assigned for participation in the study. First, the overall pattern of school attendance was analyzed. Second, a random sample of both treatment and comparison group members was assessed in terms of changes on attendance percent rates. Third, a comparison in terms of students dropping out was conducted. Finally, a cost-effectiveness analysis was utilized to examine the data. Findings support the dropout prevention intervention. Implications for practice and future research are discussed. (Contains 15 references.) (SM)