Well, Iowahawk takes them on:
As a son of Iowa, I'm no stranger to bragging about my home state's ranking on various standardized test. Like Wisconsin we Iowans usually rank near the top of the heap on average ACT/SAT scores. We are usually joined there by Minnesota, Nebraska, and the various Dakotas; Vermont, Maine, New Hampshire...
... beginning to see a pattern? Perhaps because a state's "average ACT/SAT" is, for all intents and purposes, a proxy for the percent of white people who live there. In fact, the lion's share of state-to-state variance in test scores is accounted for by differences in ethnic composition. Minority students - regardless of state residence - tend to score lower than white students on standardized test, and the higher the proportion of minority students in a state the lower its overall test scores tend to be.
Please note: this has nothing to do with innate ability or aptitude. Quite to the contrary, I believe the test gap between minority students and white students can be attributed to differences in socioeconomic status. And poverty. And yes, racism. And yes, family structure. Whatever combination of reasons, the gap exists, and it's mathematical sophistry to compare the combined average test scores in a state like Wisconsin (4% black, 4% Hispanic) with a state like Texas (12% black, 30% Hispanic).
So how to compare educational achievement between two states with such dissimilar populations? In data analysis this is usually done by treating ethnicity as a "covariate." A very simple way to do this is by comparing educational achievement between states within the same ethnic group. In other words, do black students perform better in Wisconsin than Texas? Do Hispanic students perform better in Wisconsin or Texas? White students? If Wisconsin's kids consistently beat their Texas counterparts, after controlling for ethnicity, then there's a strong case that maybe Texas schools ought to become a union shop.
Luckily, there is data on that. Who do you think comes out better? (Hint: it's not the state with the protesting, sick-leave-misusing teachers.) And in an update, Iowahawk also addresses the dropout rate statistic cited by Mr. Krugman.
Read the whole thing...it's worth it. (Language warnings generally always apply at Iowahawk.)