Kindergarten entrance age and children's achievement: impacts of state policies, family background, and peers

Using data from two cohorts of students, we present evidence that children who are relatively old when they enter kindergarten score higher on achievement tests and are less likely to repeat grades or suffer from learning disabilities than their younger classmates. These differences are driven by the accumulation of skill prior to school entry. The test score effects appear during the first few months of kindergarten, before much learning has taken place in school, and are especially pronounced among children from upper-income families. We do not find that the relationship between entrance age and outcomes reflects a heightened ability to learn or greater physical maturity among older children, the most common interpretations of the entrance age effect. The evidence also shows that having older classmates improves a child's test scores but increases the probability of grade repetition and learning disability diagnoses.