The Head Start Impact Study included a nationally representative sample of 84 grantee/delegate agencies and nearly 5,000 newly entering, eligible 3- and 4-year-old children who were randomly assigned to either: (1) a Head Start group that had access to Head Start program services or (2) a control group that did not have access to Head Start, but could enroll in other early childhood programs or non-Head Start services selected by their parents. Data collection began in fall 2002 and continued through 2008, following children from program application through the spring of their 1st grade year.
The study was designed to separately examine two cohorts of children, newly entering 3- and 4-year-olds. This design reflects the hypothesis that different program impacts may be associated with different age of entry into Head Start. Differential impacts are of particular interest in light of a trend of increased enrollment of the 3-year-olds in some grantee/delegate agencies presumably due to the growing availability of preschool options for 4-year-olds. Consequently, the study included two separate samples: a newly entering 3-year-old group (to be studied through two years of Head Start participation i.e., Head Start year and age 4 year, kindergarten, 1st grade, and 3rd grade), and a newly entering 4-year-old group (to be studied through one year of Head Start participation, kindergarten and 1st grade, and 3rd grade).
This study is unique in its design and differs from prior evaluations of early childhood programs due to the following characteristics: randomized control, a representative sample of programs and children, and the examination of a comprehensive set of outcomes over time.