The least-plausible sentence in the English language is "We know this works," when those words are spoken by President Barack Obama.

He said them in his State of the Union address about early childhood education. President Obama called for universal preschool funded by the federal government in cooperation with the states. He cited "study after study" showing that investment in Pre-K pays for itself several times over by creating better outcomes for children.

He said this about two months after the release of a devastating report on the ineffectiveness of the federal government's already-existing $8 billion-a-year Pre-K program, Head Start. The study wasn't published by The Heritage Foundation. The Kochs didn't fund it. It was conducted by the Department of Health and Human Services, which presumably doesn't have a right-wing agenda or bristle with hostility toward children.

Grover Whitehurst of the Brookings Institution calls the study "one of the most ambitious, methodologically rigorous, and expensive federal program evaluations carried out in the last quarter century." He might have added "one of the most inconvenient." Since it was released the Friday before Christmas, the best day of the year to bury bad news, even the president and his speechwriters might have missed it.

The HHS study concluded that "there were initial positive impacts from having access to Head Start, but by the end of third grade there were very few impacts ... in any of the four domains of cognitive, social-emotional, health and parenting practices. The few impacts that were found did not show a clear pattern of favorable or unfavorable impacts for children."

In other words, paraphrasing the president, "we know this program does not work." One would have thought that an elaborate, state-of-the-art study of Head Start would have merited mention in a speech advocating expansion of Head Start-like programs. One would have hoped a brave policy wonk would have piped up in the drafting process and told the president, "Uh, sir, what you are about to say about this issue is so selective as to verge on an outright lie."

Instead, the president invoked "study after study" to create an impression of empirical certainty that, at the very least, doesn't exist. He said the experience of Oklahoma and Georgia with Pre-K is that it makes it more likely kids will go on to graduate high school, hold jobs, and form stable families. Glenn Kessler, the fact-checker at The Washington Post, interviewed people close to the Oklahoma and Georgia programs, and they didn't know what the president was talking about. They are hopeful about early results, but don't have anything close to long-term returns.

Believers in Pre-K usually cite the success of the Perry Preschool Project and the Abecedarian Project, widely heralded early-childhood education programs from the 1960s and the Ô70s. But Grover Whitehurst notes what sets them apart: They were very small, lavishly funded, multi-year programs run by small teams of highly committed experts. The question is whether they can replicate them on a vast scale. The 40-year experience of Head Start, now serving 1 million children, says "no."

If the state of the research mattered to the president, he would be cautious rather than audacious in his Pre-K goals. He would focus on at-risk kids, who have the most to gain from Pre-K, rather than launching a new universal program. He would want more research on what does and doesn't work at the state level rather than declaring the question settled for all time. He would support incrementalism rather than a vast expansion on top of a failed Head Start.

But he has an ideological commitment to an expansive government and an unshakable faith in its ability, given enough funding and the right rules and regulations, to overcome any obstacle. So impervious is his point of view to the evidence that even his own Department of Health and Human Services can't penetrate it.

(c) 2013 by King Features Syndicate