Unfortunately, the evidence that preschool programs do any permanent good for such children is exceedingly weak.
Preschool advocates point to a 1960s program in Ypsilanti, Mich., and a 1970s North Carolina program called Abecedarian. Research showed those programs produced lasting gains in learning.
But no one has been able to replicate the success of these very small programs staffed by unusually dedicated people. Mass programs like Head Start staffed by more ordinary people don't work as well.
Kids in such programs seem to make no perceptible lasting gains. That's too bad, because disadvantaged kids need help.
So why is Obama emphasizing universal preschool, which would cost a lot more than preschool for the disadvantaged? The reason, I suspect, is that you would have to hire lots more credentialed teachers, which means you would get lots more teachers union members.
Teachers union leaders would love to see more dues money coming in, and to channel more to the Democratic Party.
To my suspicious eye, the preschool proposal doesn't make much sense as policy, but it makes a lot of sense as politics.
Demagoguery about preschool and corporate jets is not going to convince Republicans that Obama can be a reliable negotiating partner.
Instead, it reinforces the evidence that he never will be. This is the president who, in his grand bargain negotiations with Speaker John Boehner, agreed on $800 billion in more revenue -- and then, in a phone call, told Boehner he wanted $1.2 trillion, instead.
And it's the president who first proposed the sequester, then promised it would never happen, and then denounced it when it seemed clear it would.
We need serious changes in public policy, as Obama's Simpson-Bowles Commission recommended. But this president doesn't seem much interested in that kind of governing.