This evaluation of the 1989-90 Cumulative Deficits in Basic Skills Program (CDBSP) in Washington (District of Columbia) public schools uses achievement gains on the Comprehensive Test of Basic Skills (CTBS) and teacher use of specially developed instructional materials to assess program effectiveness. Information was gathered from an analysis of pretest-posttest scores on the CTBS of students in grades 3, 6, 8, 9, and 10 in 25 low-achieving elementary, junior high, and senior high schools. The following findings are presented: (1) students in grade 10 benefited most from the program, as indicated by overall gains in achievement; (2) students in grades 6, 8, and 9 did not benefit from the program, as indicated by overall declines in achievement; (3) the achievement of students in grade 3 did not change significantly; and (4) an analysis of the use of the specially designed instructional materials indicates that "Scoring High on the CTBS," when used by teachers in grade 10, was the most effective. Recommendations emphasize guidelines for the use of the specially designed instructional materials. Statistical data are presented in nine tables. (FMW)