The purposes of this study include: (1) determining whether socioeconomic status (SES) or verbal ability (VA) exerts greater influence on childrens' performance of Piagetian tasks; (2) devising an instrument for measuring childrens' level of cognitive development which does not depend on verbal ability alone; and (3) adapting materials for teacher use in assessing childrens' level of intellectual development. The sample was comprised of 160 low and middle SES subjects (K-4) matched for upper and lower VA, to each of whom was administered a battery of Piagetian tasks. Results indicate SES to be a negligible variable, while VA has much stronger discriminative power. Main effects for grade and verbal ability were found for all but one task, though no main effects or higher order interactions were found in connection with sex. The findings support the Piagetian position that culture, schooling, and language have only a limited effect on intellectual development. (Author/TL)