President Obama’s $75 billion preschool proposal won’t close the achievement gap, predict Brookings scholars. Sound research doesn’t show preschool makes much difference, write Russ Whitehurst and David J. Armor.
The most credible recent study of pre-K outcomes, the federal Head Start Impact Study, found only small differences at the end of the Head Start year between the performance of children randomly assigned to Head Start vs. the control group, e.g., about a month’s superiority in vocabulary for the Head Start group. There were virtually no differences between Head Start and the control group once the children were in elementary school.
Nationwide, the number of children enrolled in state pre-K programs is associated weakly with later academic performance, they write. Fourth-grade reading and math achievement “would increase by no more than about a 10th of a standard deviation if state pre-K enrollments increased dramatically.”
Advocates cite the Perry Preschool experiment “from half century ago” that is ”so different in many important ways from current state pre-K programs that findings . . . can’t be confidently generalized to the present day,” write Whitehurst and Armor.
Pre-K advocates also rely heavily on studies that don’t use random assignment of children to pre-K or a control group. “Age-cutoff regression discontinuity” studies, which show large impacts for pre-K, are “problematic,” the Brookings researchers conclude.
“There are reasons to doubt that we yet know how to design and deliver a government funded pre-K program that produces sufficiently large benefits to justify prioritizing pre-K over other investments in education.”