Easy on the cantaloupe, kids, budgets are tight. Photographer: Stephen Hilger/Bloomberg News
Easy on the cantaloupe, kids, budgets are tight. Photographer: Stephen Hilger/Bloomberg News

President Barack Obama has a costly plan to provide free preschool to every 4-year-old, and New York mayoral candidate Bill de Blasio is borrowing a page from it. The theory is that participation in "high-quality'" programs at a young age makes kids from poor backgrounds more likely to succeed as adults. Some also argue that free preschool programs help women remain in the workforce after having children. An important new study of “high-quality” universal pre-kindergarten programs by Dartmouth’s Elizabeth Cascio and Northwestern’s Diane Schanzenbach presented last week at the Brookings Institution's Panel of Economic Activity finds little evidence to support either argument, however.

Two previous studies of early-childhood education provide important context for the latest analysis. The one with the most obvious relevance is the "Head Start Impact Study," which used a randomized control trial in the mid-2000s to measure the effects of participating in Head Start. The findings aren't encouraging. According to the official report produced by the Department of Health and Human Services, “no significant impacts were found for math skills, pre-writing, children’s promotion, or teacher report of children’s school accomplishments or abilities in any year.” Researchers did find “suggestive evidence of a positive impact of access to Head Start” on vocabulary skills, although that appears to be a euphemism for a statistically insignificant result.

While the findings of the study might seem conclusive, it doesn’t directly address whether Obama’s goal of free “high-quality” preschool is worthwhile. Head Start teachers often lack college degrees, for example. Moreover, HSIS only tracked student progress through the first grade. This is why supporters of universal pre-kindergarten prefer to cite the "Perry Preschool Study," which tracked 123 children who grew up in Ypsilanti, Michigan. Researchers interviewed study participants at several points in their lives, most recently when they reached their 40th birthdays.

Experimenters split these poor (and low-IQ) children into two groups in the early 1960s. Fifty-eight of the children were put into a special preschool program, when they were 3 and 4 years old. They and their parents also received weekly home visits from teachers. The other 65 children (the “control group” in the experiment) didn't get any formal schooling until they entered kindergarten at the age of 5.

Those who benefited from this early intervention were much less likely to have been arrested and more likely to stay out of abject poverty in subsequent decades. Economists, most famously the University of Chicago’s James Heckman, have argued that these benefits -- mostly the reduction in criminal behavior -- imply a “social rate of return” of somewhere between 7 percent and 10 percent a year. That’s very high, although the dramatic decline in violent crime since 1990 suggests that the social benefits of future interventions could be much lower. Economists who participated in the discussion at the Brookings panel were skeptical that we can learn much from the Perry study given its age and its tiny sample size. They also noted that the average results were misleading because of the wide variation of individual outcomes.

Unlike these previous studies, Cascio and Schanzenbach’s analysis addresses Obama’s proposal because it evaluates the impact of universal pre-kindergarten programs in Georgia and Oklahoma, both of which were specifically cited by the president as model states. Their study found no significant lasting benefits in either program. Preschool enrollment soared -- an unsurprising result -- but student performance didn't improve. Reading scores for eighth-graders who participated in the program were unchanged, while average math scores for children who were eligible for free school lunches barely increased.

Many of the students who took advantage of the public preschools would have been in private nursery schools in the absence of the government programs. Rather than helping the genuinely disadvantaged, in other words, the state was simply transferring resources from people without children to people with children. One apparent consequence of this extra spending is a slight decline in the percentage of young mothers in the workforce, especially among women who were more educated to start with. Overall, universal pre-kindergarten programs in Georgia and Oklahoma seem to produce no effect in either direction on the female labor-participation rate.

Despite the disappointing findings on academic achievement and the extent to which middle-class families simply substitute public preschools for private ones, universal pre-kindergarten might provide some benefits. Cascio and Schanzenbach found that poor mothers seemed to spend more “quality time” with their kids as a result of these programs. That might improve the non-cognitive skills associated with lower rates of criminality, which Heckman and his colleagues deemed so important. Even if that were true, however, it seems hard to justify an expensive universal preschool program that only works to the extent that it gets a few mothers to spend slightly more time reading to their kids.

I'm sure Obama and de Blasio really want to improve opportunities for poor children, but they should ditch their plans for universal pre-kindergarten and look for more effective, less-costly ideas.

(Matthew C. Klein is a writer for Bloomberg View. Follow him on Twitter.)