Hart & Risley,
positive family interaction with infants to age 4: long-term positive impact
compare and contrast with
Head Start,
pre-school for 3-year-olds and 4-year-olds: gains even out by third grade.
This is the longitudinal study by the U.S. Department of Health & Human Services (HHS), Administration for Children & Families (ACF), Office of Planning, Research, and Evaluation (OPRE). One of the report links on this webpage is the Executive Summary for the "
Third Grade Follow-up to Head Start Impact Study", and states, in part:
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.
...
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.
Archived Links:
1) Head Start impact summary, follow-up - https://web.archive.org/web/20160309043339/http://www.acf.hhs.gov/programs/opre/research/project/head-start-impact-study-and-follow-up
2) 32-page PDF, executive summary - https://web.archive.org/web/20170201141546/http://www.acf.hhs.gov/sites/default/files/opre/head_start_executive_summary.pdf
