This document, a two-volume report, provides in volume 1 the final longitudinal evaluation of the New York City Dropout Prevention Initiative (DPI), 1985-86 through 1987-88. (The second volume comprises appendices containing summaries of each previous evaluation for this time period.) The DPI was implemented in 13 high schools and 29 feeder middle schools to stimulate systemic interventions in the high schools and experiment with the use of community-based organizations (CBOs) at both levels. The program targeted a yearly average of 4,335 middle school students and 5,510 high school students with high absenteeism, course failure, and/or a principal's recommendation that they were at-risk. The following services were provided: (1) program facilitation; (2) attendance outreach; (3) guidance and counseling; (4) health services; (5) linkages between middle and high schools; (6) alternative education programs; and (7) increased school security. Overall, the DPI did not improve attendance or the number of courses passed, and probably did not reduce the number of dropouts. Furthermore, there were no consistent differences found between outcomes for students in schools served by CBOs and those served by other staff. The total program cost $40 million, and the average cost per student for one year was over $1,000 in the middle schools and over $1,500 in the high schools. Recommendations for improvement emphasize a comprehensive restructuring of the school experience. Statistical data are included on 38 tables and 35 graphs. (FMW)