I was glad to see Kevin Drum pull out the NAEP TUDA data yesterday so we can see how Chicago Public School students are actually doing and the answer turns out to be below-average but steadily improving. Indeed, if not for the fact that students in other big city districts are also doing better, Chicago would have moved from below-average to above-average. And this is before we account for compositional effects. Kids whose parents don't have much education and who may not speak English natively are at a serious disadvantage in schools, and in Chicago and elsewhere those kind of cases have been a growing share of the student population.
The political valence of this basic point is always a bit hard for me to puzzle out. On the one hand "reformers" have a longstanding habit of massively overstating the scale of the problems in the US school system. On the other hand, Chicago and many other big cities has been primarily under a "reform" regime for most of this time. So you can look at the data and say either that the reformers ought to chill out or else that the reformers are vindicated. What seems most persuasive is probably going to depend almost entirely on your priors. But in general, looking at the data should give you a more optimistic look at the American future. The 2002-2003 cohorts of 8th graders are in their mid-twenties now, but there's reason to believe the next cohort of workers will show up with better skills.