The following is cross-posted from the National Journal’s Education Experts blog:

This week’s introduction says that, when it comes to President Obama’s preschool proposal, “the only problem, as always, is that these investments cost money.” These proposals certainly would cost money – dollars Washington doesn’t have – but even discussing cost is seriously jumping the gun. The fact is that right now, regardless of cost, there is almost no meaningful evidence to support massive expansion of federal pre-school efforts. Indeed, the evidence calls much more loudly for the opposite.

Start with the biggest federal pre‑K initiative, Head Start. It costs about $8 billion per year, and what are its lasting effects? According to the latest random-assignment, federal assessments, there essentially aren’t any. The program has demonstrated no meaningful, lasting benefits, and is therefore a failure.

How about Early Head Start, which involves children ages 0 to 3? It is a much newer program than its big brother, but it, too, provides no evidence of overall, lasting benefits. As a 2010 random-assignment, federal study concludes:

The impact analyses show that for the overall sample, the positive effects of Early Head Start for children and parents did not continue when children were in fifth grade…. It appears that the modest impacts across multiple domains that were observed in earlier waves of follow-up did not persist by the time children were in fifth grade.

There were, to be fair, some lasting positive effects found for some subgroups, but there were also negative effects. And for the “highest-risk” children – the ones the program is most supposed to help – the outcomes were awful:

Finally, for children in the highest-risk group, six impacts were statistically significant, all of which were at the child level and all of which favored the control group. Children in the program group scored significantly lower than children in the control group on the PPVT-III (ES = −0.21, p < .10) and the mathematics test (ES = −0.33, p < .05) and had lower scores on the academic success index (ES = −0.29, p< .05). Parents reports indicated that chronic absenteeism was higher in the program group than the control group (ES = 0.37, p < .10). Children in the program group also scored higher on the cumulative risk index (ES = 0.35, p < .10) and lower on the cumulative success index (ES = −0.31, p < .05) than children in the control group. There were no significant impacts on parenting and family-level outcomes in the highest-risk group.

The federal government, quite simply, has demonstrated no ability to scale-up pre‑k programs and achieve positive, lasting effects. Knowing that, it is impossible to convincingly argue that the current efforts should even be maintained, much less greatly expanded.

What about state programs? The evidence is hardly conclusive that even highly-touted programs such as those in Oklahoma or New Jersey are effective. The quality of the research – which is rarely random-assignment – isn’t what it needs to be to confidently conclude that the programs work. Indeed, pre‑K advocate James Heckman said that in a Washington Post interview:

Dylan Matthews: The Abecedarian and Perry experiments provide pretty definitive evidence that individual preschool programs have strong effects, but Obama’s been touting certain statewide programs like Oklahoma’s. What’s the evidence for those like?

James Heckman: I would be cautious. I’m instinctively cautious because I’m an academic. The Perry and ABC (Abecedarian) and some others, the nurse-family partnership, have not only had randomized trials, but have also followed people up for decades. The Perry people are now 50 years old. The ABC people, now they’re close to 40. We actually can follow them in a way that the other programs don’t follow their participants. The state programs have relatively short-term evaluation plans. And I think, you’re right, they’re not randomized controlled trials, so I’m a little cautious. I don’t find them as convincing. As far as I know they’re not of the same quality. I have not personally relied on them. That’s not to say they’re bad programs, they just haven’t been evaluated as thoroughly.

So state programs haven’t been adequately evaluated to demonstrate their effectiveness, yet some act like it is obvious that the federal government – which has demonstrated an inability to run effective pre‑K programs – should scale all this up. Illogical. What they should be insisting is that Washington follow the Constitution and stay out of this, letting states experiment to see what works and what doesn’t, and replicate programs on their own – or do nothing – if they think the evidence justifies it.

When you get down to it, there are only two or three pre‑K programs that have solid enough research bases that advocates can confidently say they had lasting, positive effects. As Dylan Matthews’ question makes clear, the two most prominent are the Abecedarian and Perry Preschool programs. But here’s what you need to know: Both were hyper-intensive programs with very dedicated staff. Indeed, Abecedarian treated just 57 children at a price of about $17,700 per child, and Perry worked with 58 kids at roughly $12,500 per child. For all intents and purposes there is no way any government is going to scale those up and get the same effects, much less the bloated, ineffectual federal government.

It is much too early to say the only reason not to expand federal per‑K is the lack of funds. Before anyone gets even close to that, they need to address the huge dearth of evidence that big pre‑K – especially federal – would be anything other than a failure.