According to the latest buzz, President Obama may suggest dramatically expanding federal government preschool programs in his State of the Union address next week. That, at any rate, is the recommendation of a new report from an institute closely associated with the admnistration.

There are just two problems with this plan: 1) it’s already been tried; 2) it doesn’t work.

We now have 45 years of experience with, and two top-quality randomized studies of, the national Head Start pre-school program, and the results are disappointing. Head Start was meant to close the gap in student achievement between the children of advantaged and disadvantaged families. But, at the end of high school, the gap in achievement between the children of college graduates and those of high school dropouts has remained essentially unchanged since the program was introduced. We have even more direct evidence from two large national studies of the program commissioned by the very agency that administers it: the Department of Health and Human Services. These studies find no significant benefits to Head Start at the end of the third grade–or even at the end of the first.

So why double-down on a failed program? The most plausible (and charitable) explanation is a bad case of wishful thinking. Many people make the mistake of improperly generalizing from two or three tiny pre-school programs of earlier decades which did show some lasting benefits. Sadly the federal government’s nationwide Head Start program has not replicated those benefits despite generations of unrelenting effort. And there is no reason to imagine that it will suddenly start doing so if expanded even further.

Trying to fix failed federal preschool programs by dumping more money on them is like trying to make up per-unit losses by increasing sales volume. Sadly, that’s about the level of economic acumen demonstrated by recent administrations.