NCLB Missing on the Margins

Last week’s most-clicked story, via ASCD’s SmartBrief:

NCLB Seen as Curbing Low, High Achievers’ Gains:
Is NCLB leaving behind students at the lowest and highest ends of the achievement spectrum? A new study out of the University of Chicago shows students in the middle make the largest gains, under NCLB, while gifted students stagnate, and the lowest achievers may even lose ground.

Does NCLB disproportionately serve middle-achievers? Is it too soon to tell?

Does this study, as AEI’s Charles Murray claims, “strike a major blow to proficiency counts as a measure of progress in education”?