A 2011 report issued by the Department of Health and Human Services concluded that “the benefits of access to Head Start at age four are largely absent by first grade for the program population as a whole. For 3-year-olds, there are few sustained benefits, although access to the program may lead to improved parent-child relationships through 1st grade, a potentially important finding for children’s longer term development.”

That report, and others, has caused some lawmakers to question the value of enhanced pre-K.

“Most importantly, will this plan be effective?” asked Rep. John Kline (R-Min.), chairman of the House Education and the Workforce Committee. “The federal government has a poor track record of managing early childhood education initiatives, with mounting evidence that Head Start may not be helping students as much as we had hoped.”

Kline said he is willing to have “a serious dialogue” with administration officials “if they are willing to offer less rhetoric and more facts.”

“I am confident we can find ways to promote parental choice, ensure an appropriate federal role in education and serve our nation’s most vulnerable youth – without offering more empty promises to our children or adding more debt onto the backs of taxpayers,” Kline said.

Some education experts dismissed the administration’s initiative.

“The trouble with federal-government-funded preschooling is that we have 47 years of experience with it — and it doesn’t work,” said Andrew J. Coulson, director of the Center for Educational Freedom at the Cato Institute. “The federal Head Start pre-K program was created in 1965, and, despite decades of concerted efforts to refine and improve it, it has virtually no measurable effects that last to the end of the third grade—or even the first.”

Of the very few and modest effects that have been found at the end of the third grade, Coulson said, some are actually negative.

“That is what federal government pre-K has accomplished with $200 billion and half a century of effort,” he said. “Is that a sensible basis for expanding federal government pre-K?”

But proponents cite the results of other studies, particularly the Perry Preschool Project, as evidence establishing the worthiness of early childhood education. That study was based on 3- and 4-year-old students who attended a preschool program at Perry Elementary School in Ypsilanti, Mich., in the early 1960s, tracing their development over decades and comparing their outcomes to other children who did not attend preschool.

The study found, among other things, that the Perry group had a higher high school graduation rate, were less likely to serve time in prison, experienced fewer out-of-wedlock births, experienced a higher median monthly income, and were less likely to receive government assistance. It further determined that every dollar spent on preschool education resulted in a $16 return.

Researchers from the Frank Porter Graham Child Development Institute at University of North Carolina recently looked into the pre-K program in Georgia, one of the few states offering universal access and generally considered one of the nation’s best.

“Children in Georgia’s pre-K program exhibited significant growth during their pre-K year across all domains of learning: language and literacy skills, math skills, general knowledge and behavioral skills,” said Ellen Peisner-Feinberg, the project’s senior scientist. “For many areas, this indicated that they progressed at an even faster rate than would be expected for normal developmental growth.”

Peisner-Feinberg’s team also determined that Georgia’s program was valuable to children who were Spanish-speaking dual-language learners. “They made gains in both English and Spanish, even though the primary language of instruction was English,” she said.

North Carolina, which offers a state program targeting low-income students, also has shown positive results. Known as the Abecedarian Project, it determined that by age 21, participants earned higher reading and mathematics test scores, had a greater likelihood of being enrolled in college, and were less likely to become teen parents.

Still, some who have questions about the efficacy of the Obama proposal, like Whitehurst at Brookings, maintain there exists a dearth of research into the subject and what there is offers a mixed bag, characterizing the Georgia study as showing preschool provides “impacts that are at best very small and do not pass a cost-benefit test.”

“This thin empirical gruel will not satisfy policymakers who want to practice evidence-based education,” he said.