The comparative school readiness and cognitive ability of kindergarten children from lower-income schools (N=47) and from higher-income schools (N=71) were assessed using the Preschool Inventory and a battery of eight Piagetian tasks. The overall purpose of the study was to ascertain characteristics of the children's cognitive development as a basis for subsequent examination of kindergarten curriculum programs in the Paradise Valley Unified School District of Arizona. There was a concern within the District that differences in maturity, experience, and achievement might exist between children attending Title I schools and children attending schools not meeting the eligibility requirements for Title I. Results indicated that all children performed within the high range of normal scores on the Preschool Inventory. The lower-income group had a mean score of 54 (range, 28-64) and the higher-income group a mean score of 57 (range, 42-64). This difference, although statistically significant, was considered to be an artifact of measurement. For the measures of cognitive ability, the two groups' performances did not differ significantly on conservation, seriation, or spatial relationships tasks. The high-income group scored significantly higher than the lower-income group, however, on classification tasks. (Author/SS)