Kelsey Piper has written an article for Vox: Early Childhood Education Yields Big Benefits – Just Not The Ones You Think.

I had previously followed various studies that showed that preschool does not increase academic skill, academic achievement, or IQ, and concluded that it was useless. In fact, this had become a rallying point of movement for evidence-based social interventions; the continuing popular support for preschool proved that people were morons who didn't care about science. I don't think I ever said this aloud, but I believed it in my heart.

I talked to Kelsey about some of the research for her article, and independently came to the same conclusion: despite the earlier studies of achievement being accurate, preschools (including the much-maligned Head Start) do seem to help children in subtler ways that only show up years later. Children who have been to preschool seem to stay in school longer, get better jobs, commit less crime, and require less welfare. The thing most of the early studies were looking for – academic ability – is one of the only things it doesn't affect.

This suggests that preschool is beneficial not because of the curriculum or because of "teaching young brains how to learn" or anything like that, but for purely social reasons. Kelsey reviews some evidence that it might improve child health, but this doesn't seem to be the biggest part of the effect. Instead, she thinks that it frees low-income parents from childcare duties, lets them get better jobs (or in the case of mothers, sometimes lets them get a job at all), and improves parents' human capital, with all the relevant follow-on effects. More speculatively, if the home environment is unusually bad, it gives the child a little while outside the home environment, and socializes them into a "normal" way of life. I'll discuss a slightly more fleshed-out model of this in an upcoming post.

My only caveat in agreeing with this perspective is that Chetty finds the same effect (no academic gains, but large life-outcome gains years later) from children having good rather than bad elementary school teachers. This doesn't make sense in the context of freeing up parents' time to get better jobs, or of getting children out of a bad home environment. It might make sense in terms of socializing them, though I would hate to have to sketch out a model of how that works. But since the teacher data and the Head Start data agree, that gives me more reason to think both are right.

I can't remember ever making a post about how Head Start was useless, but I definitely thought that, and to learn otherwise is a big update for me. I've written before about how when you make an update of that scale, it's important to publicly admit error before going on to justify yourself or say why you should be excused as basically right in principle or whatever, so let me say it: I was wrong about Head Start.

That having been said, on to the self-justifications and excuses