The latest Bloomberg Businessweek features an article on Nobel Prize-winning economist James Heckman’s advocacy for increased taxpayer funding of prekindergarten programs. Read just the headline (especially the online version’s declaration that “Early Childhood Education Benefits All”), and you’re likely to miss an interesting caveat included near the end of the piece.

“If there are people who disagree with Jim Heckman,” [Harvard University economist David Deming] says, it’s because they doubt that “one experiment with 100 kids in Ypsilanti gives you the information you need.” Heckman concedes the early studies are showing their age. But more recent research on programs from other states “has one major flaw—no long-term follow-up,” he says. “I’m not going to argue that those things might not work, but we can’t argue yet that they have.”

It’s also not clear whether spending on middle-class children yields the same return as it does for poor kids. “A lot of this eye-popping benefit comes from crime reduction,” says Deming, and children from better-off families are less likely to commit crimes with or without early education. Heckman agrees. For that reason he stops short of endorsing universal pre-K. As a matter of politics, though, any education program must include the middle class. “Reality is, if you target a program at the very poor, it’s hard to build political support,” says Duncan.

Heckman’s research doesn’t lead him to endorse any single early education proposal. “The idea of a uniform curriculum is insane,” he says. “There’s this notion of objective public policy. Everyone signs off, and governors give away fountain pens,” he says, but each state has different needs. Regardless of the curriculum a state adopts, the long-term savings his research promises come from providing intense, parenting-style attention to the children who can most benefit from it. “The most successful programs,” he says, “would mirror what’s going on in the most successful families.”

Taxpayer-funded pre-K makes more sense for poor kids than for middle-class kids? Hmm. Perhaps eligibility for NC Pre-K should be narrowed to focus primarily on low-income children.