HHS study suggests Head Start programs have little effect by 3rd grade [pdf]

From the actual report:

Key Findings Looking across the full study period, from the beginning of Head Start through 3rd grade, the evidence is clear that access to Head Start improved children’s preschool outcomes across developmental domains, but had few impacts on children in kindergarten through 3rd grade. Providing access to Head Start was found to have a positive impact on the types and quality of preschool programs that children attended, with the study finding statistically significant differences between the Head Start group and the control group on every measure of children’s preschool experiences in the first year of the study. In contrast, there was little rd evidence of systematic differences in children’s elementary school experiences through 3 grade, between children provided access to Head Start and their counterparts in the control group. In terms of children’s well-being, there is also clear evidence that access to Head Start had an impact on children’s language and literacy development while children were in Head Start. These effects, albeit modest in magnitude, were found for both age cohorts during their first year of admission to the Head Start program. However, these early effects rapidly dissipated in elementary school, with only a single impact remaining at the end of 3rd grade for children in each age cohort. With regard to children’s social-emotional development, the results differed by age cohort and by the person describing the child’s behavior. For children in the 4-year-old cohort, there were no observed impacts through the end of kindergarten but favorable impacts reported by parents and unfavorable impacts reported by teachers emerged at the end of 1st and 3rd grades. One unfavorable impact on the children’s self-report emerged at the end of 3rd grade. In contrast to the 4-year-old cohort, for the 3-year-old cohort there were favorable impacts on parent- reported social emotional outcomes in the early years of the study that continued into early elementary school. However, there were no impacts on teacher-reported measures of social- emotional development for the 3-year-old cohort at any data collection point or on the children’s self-reports in 3rd grade.

There is evidence that for some outcomes, Head Start had a differential impact for some subgroups of children over others. At the end of 3rd grade for the 3-year-old cohort, the most striking sustained subgroup findings were found in the cognitive domain for children from high risk households as well as for children of parents who reported no depressive symptoms. Among the 4-year-olds, sustained benefits were experienced by children of parents who reported mild depressive symptoms, severe depressive symptoms, and Black children.