The 1983-84 Preparation for Raising Educational Performance (PREP) program was a theme-based program of instruction and supportive services for incoming ninth graders who are substantially below grade level in reading and mathematics. PREP was offered in 91 public high schools in New York City and provided services for nearly 12,000 students. Students scoring between 5.1 and 7.1 in reading grade equivalents or below the 6.6 grade level in mathematics were in PREP A and students scoring at or below the 5.0 grade level in reading were in PREP B. The theme-related classes were designed to improve students' basic skills and strengthen their perception of the relationship between academic success and future careers. Themes included: Careers; Computers; High Technology and the Future; and Communication and the Arts. Program goals for attendance and attitudes toward school were met. Overall achievement gains of PREP students were eight months in reading and six months in mathematics. PREP B students made significantly higher gains than PREP A students. Analyses suggest that the program was most effective with students below grade level in only one skill area and with those who were far below grade level in both skills areas. Staff training was limited, and academic teachers had difficulty integrating the PREP themes into courses, while vocational teachers found it hard to integrate skills instruction. Major recommendations for program improvement are: (1) extend PREP eligibility criteria; (2) consider aiding schools in developing themes that are clearly goal oriented; (3) give schools assistance in setting up block programs that are well developed and successful; (4) give teachers time for planning and articulation through scheduling and common free periods. (CG)