Preschoolers in a model preschool designed to develop children's planning and problem-solving abilities were compared to children in three comparison preschools on measures assessing children's ability to solve problems and plan. Children were also compared on other measures of cognitive ability, including measures of general cognitive functioning, vocabulary IQ, and Piagetian developmental level. All children attended private, suburban, middle-class preschool programs. Findings indicated that children participating in a model preschool designed to develop planning and problem-solving abilities scored significantly higher than children in comparison preschools on measures constructed to assess those abilities. No differences between preschools were found on the other, more diverse measures of cognitive ability. (RH)