"Though you would never know it from the state of public alarm about education, the numbers show that regular public school performance has skyrocketed in the last two decades to the point that, for example, black elementary school students now have better math skills than whites had only 20 years ago. (There has also been progress for middle schoolers, and in reading; and less, but not insubstantial, progress for high schoolers.) The reason test score gaps have barely narrowed is that white students have also improved, at least at the elementary and middle school levels. The causes of these truly spectacular gains are unknown, but they are probably inconsistent with the idea that typical inner-city teachers are content to watch students wrestle on the classroom floor instead of learning."
—This critique of Steven Brill's Let's Blame The Teacher Unions is worth your time.