One general observation I'd make is that when reading news stories about how "30% of US high school graduates can't find the US on a world map", it's wise to remember Mark Twain's aphorism: There are lies; there are damned lies; and then there are statistics.
Different people with different agendas have different reasons to manipulate statistical numbers about educational performance -- sometimes making the students look better than they really are; sometimes making them look worse. For example, the claim that N% can't find their own city/state/country on a map!!! is an "Evergreen" topic for newspaper editorialists, because it's always guaranteed to generate letters from ordinary citizens as well as from officials and politicians, with everyone proposing his "pet" solution to the problem.
Stereotypically, those on the left may exaggerate illiteracy figures in order to argue that we need to spend less on fighter planes and more on public schools; while those on the right may also exaggerate the problem, in order to argue that the public education system is corrupted by teachers' unions and that we should spend more tax money on public-school alternatives (such as "voucher coupons" that poor families can use to send their kids to private schools).
But note that both sides quote the same frightening statistic that 1 out of 4 students don't know such-and-such! (In other contexts, the picture painted is overly rosy, instead of overly gloomy, depending on the argument.)
I don't have a strong opinion on this, though anecdotally, I've met quite a few college-educated African-American adults from lower-class backgrounds who attribute their success to the fact that their parents somehow or other managed to send them to Catholic schools instead of urban public schools.