Effective schools provide at-risk students with a community of support that encourages school membership and educational engagement. This study describes effective dropout prevention programs, develops a generalizable, theoretical framework for understanding the relationship between at-risk students and their schools, and suggests local and state policy changes to improve schools. Data were gathered from site visits to 14 secondary schools selected on the basis of their successful dropout prevention programs. Key findings include the following: (1) successful schools created a supportive environment that helped students overcome impediments to membership and engagement; (2) impediments to engagement include absence of economic pay-off after graduation, a narrow conceptualization of learning, and a superficial curriculum; (3) successful programs matched student needs and problems, and took advantage of student interests and strengths; and (4) the teachers at successful schools accept a proactive moral responsibility for educating at-risk youth. Suggestions for improvement focus on encouraging alternatives for at-risk youth, the need for a systematic approach to school reform, and the establishment of community partnership strategies. Thirteen tables of statistical data and a chart illustrating the school factors involved in dropout prevention are included. The appendices comprise descriptions of the 14 schools studied and a discussion of the research methodology employed. An index and a list of 83 references are also included. (FMW)