From today's NYT:
This article notes that while Black and Hispanic students at the elementary, middle and high school levels scored much higher on the "National Assessment of Educational Progress" (a federal test "considered to be the nation's best measure of long-term trends in math and reading proficiency") than they did 30 years ago, most of the gains were made during desegregation efforts in the 70's and 80's.
In recent years (2004 to the present) scores for both minority and white students increased, leaving the achievement gap in place. Further, these gains do not seem attributable to NCLB. One expert noted that "Trends after the law took effect mimic trends we were seeing before."