From the blog post:
As millions of parents across the United States are getting their children back to school, academics and policymakers are also taking a closer look where it all begins for the nation’s earliest learners — preschool. Does it really work and is it worth the cost? ….
…. The question may be simple, but the answer is less so.
Early studies of Head Start and other preschool programs found large positive effects on both cognitive and non-cognitive skills, like vocabulary and self-control. But the first randomized experimental study of Head Start (the Head Start Impact Study, or HSIS), conducted in 2002, showed that the program produced smaller benefits that faded out by the time the students were in third grade. Some have interpreted this as evidence that Head Start is ineffective.
Several recent studies by UC Berkeley faculty and others, however, have shown that the HSIS data, when interpreted appropriately, indicates that Head Start has significant benefits. Some of these benefits last far beyond the Head Start years, like increases in health and lifetime earnings.
The reason for this misinterpretation is simple: unlike earlier studies, the HSIS compared Head Start participants to children in a broad range of childcare arrangements, many quite similar to Head Start. About one-third of the HSIS control group participated in alternative preschool programs, and the rest of the children in the control group were cared for at home…..