Kevin Drum says "[w]e'd be better off with 100 percent more pre-K and 20 percent less K-12 than we are with our current funding priorities."
I'm not so certain this is true. I think a lot of the thinking about the efficacy of pre-K education is based on looking at the best performing programs while thinking about K-12 tends to be informed by thinking about the typical program. But in both cases quality matters. The best charter school networks in America really do seem to be incredibly effective at teaching children, but as charter school critics point out the average charter school's performance is merely average. The pre-K results look pretty similar to me. The best programs get amazing results, but lots of programs are non-amazing in practice.
This is, however, a political tradeoff that I think is interesting. Critics of the "education reform" movement tend to emphasize the idea that K-12 learning outcomes are largely socioeconomically fixed, and to tout the benefits of early childhood education and poverty reduction efforts. If your view of K-12 is that those kind of things—rather than shaking up the management of K-12 schools—are the best way to improve education, then it seems like the Drum hypothesis should be attractive.