The Obama administration has made pre-kindergarten programs a national priority. The theory is that if society better equips children to learn, they will do better in school and in life.
But so far, the evidence that pre-kindergarten programs produce results is underwhelming. The latest assessment comes from Vanderbilt University study.
Tennessee spends $86 million a year on preschool programs to serve about 18,000 low-income 4-year-olds. The state is eligible for $64.3 million in federal funds for pre-kindergarten programs to 7,681 more children.
But to get $64.3 million from the federal Preschool for All program, Tennessee Gov. Bill Haslam and state budgeters would have to come up with $6.4 million in state matching funds each year.
State officials wanted to see the results of the Vanderbilt study before making a decision.
"The highly anticipated findings say more strongly than ever that Tennessee children who make big gains in math, language and reading by attending prekindergarten don't stay ahead of their peers - perhaps not even through kindergarten," wrote Tony Gonzalez of The Tennessean.
"By the end of first grade, the differences in abilities all but evaporated - a surprisingly fast leveling off, researchers found," he wrote.
But the Vanderbilt team did see some behavioral differences that could make a difference in the long run.
Kids who went to preschool were promoted from kindergarten to first grade at twice the rate of kids who did not attend preschool, and had better first-grade attendance records.
"A lot of what matters for kids - particularly these high-risk kids who are the focus of the pre-K program - . . . is hanging in there in school," said Mark Lipsey, director of Vanderbilt's Peabody Research Institute.
Still, states must balance many important needs.
A preschool funded is a highway not built, a doctor not paid or a prison not properly staffed.
It would be easier to justify spending $6 million more a year on prekindergarten - $60 million more every decade - if there were more tangible evidence that it produced great progress.