The prediction of achievement provides teachers with necessary information to help children attain optimal achievement. If some skill prerequistites to learning which are not fully developed can be identified and strengthened, higher levels of achievement may result. The Metropolitan Readiness Tests (MRT) are routinely given to all University City kindergarten children. The test of Primary Mental Abilities (PMA) was then administered to groups of boys and girls who were reasonably representative of children in University City Schools in the second month of first grade, and the Stanford Achievement Test at the end of first grade. Analyses of the data revealed similarities and differences in the effectiveness of these tests in predicting performance, measured by subtests of the Stanford Achievement Test, seven to thirteen months later. Both tests identified abilities and guided teachers in individualizing programs based on a child's developmental needs. However, the MRT were more applicable to boys, the PMA to girls. The use of the scores on both tests together added very little to their predictive value; the PMA test hs a slight advantage over the MRT if one had to select a single test. (Author/PR)