This longitudinal study investigates the relationship between preschool children's ability test scores and their scores on achievement tests in 1st and 2nd grade. Subjects were 59 academically able children (27 boys and 32 girls, 4 black and 55 white) enrolled in an independent school. Children (mean age, 3 years, 9.8 months) were assessed with the McCarthy Scales of Children's Abilities. Each mean McCarthy Scale score obtained for the study children was within one standard deviation of the standardized means. When the subjects were in the 1st grade, Level 1, Form A of the Comprehensive Testing Program of the Educational Records Bureau (ERB) was administered. In the 2nd grade, Level 2, Form B was used. Pearson correlation coefficients indicated that correlations between McCarthy Scale scores and 2nd grade achievement test scores were larger than the correlations between McCarthy Scale scores and first grade achievement test scores. While additional studies of the relation between the McCarthy Scales and achievement measures are needed, the study adds support to the notion that the McCarthy Scales are valid predictors of school achievement. (Author/RH)