The Head Start Impact Study looked at three and four year olds applying for Head Start in 2002 and compared children who were told they could enroll with those told they couldn't. At the end of the Head Start year there were significant benefits for the Head Start children in every domain measured. By the end of third grade, after four years in the same public school settings as their peers, the Head Start children as a whole showed few differences on academic measures. Yet deeper and more targeted analyses of Head Start Impact Study data over the last few years have actually taught us a great deal more about how Head Start works best and for whom. As Nobel Laureate Economist James Heckman has written, "The bottom line: a wide range of studies show that disadvantaged children benefit from access to quality early childhood programs—and society benefits from targeted investments in disadvantaged children. Other findings provide clarity on a number of contentious issues: Head Start Works."
The Head Start Impact Study was mandated by Congress in 1998 and overseen by the Office of Planning, Research, and Evaluation. Using an “Intent to Treat” model, the study compared children who were told they could enroll with those told they couldn't, which typically leads to weaker findings because not all children participate in their assigned settings. Exhibit 1 of the Head Start Impact Study Final Report (at right) illustrates the high rates of participation of control group children in Head Start – nearly half of the 3 year olds in the control group attended Head Start when they were 4. Beyond the significant mixing between the two groups, children who did not attend Head Start went to a wide range of both high and low quality settings, yet at the end of the Head Start year there were significant benefits for the Head Start children in every domain measured.
By the end of third grade, the Head Start children as a whole showed few differences from the control group children on the assessments used. However, these findings reflect the results of the best-known longitudinal studies of early childhood programming. In From Preschool to Prosperity, economist Timothy Bartik lays out a comparison of familiar early childhood studies: model programs Abecedarian and Perry Preschool, both of which included more years of more intensive services than Head Start children in the Impact Study received, follow a similar pattern of impacts. (Reproduced with the author’s permission.) For all these programs, the benefits of early education which appear to dissipate on standardized tests in grade school reemerge in adulthood through increased adult earnings, perhaps because long-term benefits are mediated by family stability or social-emotional strengths that are not assessed on third grade tests. It is also likely that Head Start outcomes are stronger now, nearly 15 years after data collection for the Impact Study, because of efforts to strengthen the program. One such effort has nearly doubled the proportion of BA Head Start teachers from 38% at the time of the study to 73% in 2015.
Yet even as the broad findings of the Head Start Impact Study suggest impacts dissipate during elementary school, deeper and more targeted analyses of Head Start Impact Study data over the last few years have taught us a great deal more about how Head Start works best and for whom.
Since 2002, major changes to Head Start through the 2007 reauthorization have strengthened Head Start's standards, teachers, and curricula. As a result, today's impacts are likely stronger and more consistent across the country. Local efforts to track children’s outcomes have found strong school readiness outcomes and sustained impacts.
Over the past fifty years, more than thirty-two million children and their families have had stronger academic, health, and social outcomes because of Head Start. Ensuring all Head Start programs have the staff and resources necessary to reach the highest quality will enable every community to keep the window of opportunity alive for all children.