The objective of this study was to assess the ability of a previously prepared diagnostic test to detect the need for remediation in preschool children and then to assess the effectiveness of specially designed remedial materials. The subjects consisted of 47 boys and 25 girls from four private kindergartens in Nashville, Tennessee. All subjects were given the Metropolitan Readiness Test and the diagnostic test. Subjects scoring in the lower one-half of each class on the diagnostic test were randomly assigned to experimental and control groups; each group contained four subjects (N=32). The experimental groups received eight one-half hour training sessions on basic Piagetian concepts. After completion of the training, parallel forms of both pretests were administered and the results analyzed by analysis of covariance; pretest (covariate) correlated above 0.6 with posttest (criterion). This analysis indicated a significant treatment effect (alpha = 0.05), in favor of the experimental group, on the Metropolitan Test. On the diagnostic test, the experimental group's increase in mean score was greater than the control group's increase. There was a significant treatment by school interaction which was interpreted as indicating that the treatment had different effects in different schools. (Author/JP)