A study investigated how children's constitutional temperament (Easy, Difficult, or Intermediate), measured at 18 months of age, influences their adaptation to formal schooling. Information was collected from 35 children and their parents who were part of a longitudinal study of development. All participants were first-born children from Euro-American, upper-middle class, two-parent families in a midwestern suburb. Parental reports of toddler temperament were obtained using the Toddler Temperament Scale. Several measures were used as pre- and post-Kindergarten assessments. Mixed factorial analyses of variance revealed that children with Easy temperaments adapted well to kindergarten, showing gains in IQ and academic achievement, and maintaining their levels of adaptive behavior. Children with Difficult temperaments, on the other hand, adapted poorly, showing declines in IQ and adaptive behavior. Findings suggest that there is a relationship between early childhood temperament ratings and both cognitive and behavioral skills at school entry. (HTH)