Head Start Impact Study
US Department of Health and Human Services · United States (nationally representative) · 2002
Summary
The Head Start Impact Study is one of the most politically contentious education evaluations in US history. Children gained meaningfully during the Head Start year—reading skills, vocabulary, attention. But by first grade, the cognitive gains had largely faded to insignificance. Critics cited this as evidence of Head Start's ineffectiveness. Defenders noted that children subsequently attended the same low-quality schools, erasing gains that high-quality K–12 could sustain. Health and parenting outcomes did persist. The debate over 'fade-out'—whether gains from early programs disappear or are masked by poor subsequent schooling—remains active, making this study essential context for any early childhood policy discussion.
Research question
"What is the causal impact of access to Head Start on children's cognitive, social-emotional, and health outcomes?"
Methodology
Intervention
Lottery-based access to Head Start preschool for 3- and 4-year-old children from low-income families
Assignment
Oversubscription lottery (randomized at program level)
Sample size
4,667 children (2,559 treatment, 2,108 control) across 84 programs
Primary outcome
School readiness, cognitive skills, health outcomes, social-emotional development
Effect estimate
Age 3 cohort: meaningful reading/literacy gains by end of program year; by 1st grade: no significant cognitive differences; 3rd grade follow-up: minimal lasting impacts; some positive health and parenting effects persisted
Decision
Program retained due to health, nutrition, and parenting components; research community debated whether 'fade-out' reflects program quality or school quality after Head Start
Result
Mixed
Age 3 cohort: meaningful reading/literacy gains by end of program year; by 1st grade: no significant cognitive differences; 3rd grade follow-up: minimal lasting impacts; some positive health and parenting effects persisted
Evidence strength
Moderate
Randomized trial; replication status unknown or limited.
Replication status
N/A
Institution
US Department of Health and Human Services
Location
United States (nationally representative)
Year
2002
Policy area
Public Health
Mechanism
Human capital