The effectiveness of the Elementary and Secondary Education Act Title I reading and mathematics laboratories were evaluated to assess the improvement of underachieving elementary school students' academic skills. Laboratory students were selected on the basis of academic (rather than socioeconomic) criteria in grades 2 through 5; the control groups were selected from non-Title I schools. Dependent variables were total reading and total mathematics scores on the Comprehensive Tests of Basic Skills (CTBS). Relative effectiveness of laboratory conditions was analyzed for each grade by analysis of covariance on the spring CTBS scores with the fall scores as covariate and group assignment as experimental treatment. It was determined that there was no statistically significant superiority of laboratory groups, except for fourth grade reading and mathematics in 1977-78 and third grade reading and fifth grade mathematics in 1976-77. CTBS scores were best predicted from the previous fall test administration. (Author/MH)