The entire concept of the "achievement gap" has always struck me as ill-conceived since if underprivileged youth managed to match their betters' achievement via hard work, long hours and superlative schooling, there is no reason to think the privileged classes would not respond by adopting the same measures themselves on top of their perennial advantages. Or, more likely, moving the goalposts, changing the rules or just undermining poor and minority kids directly.
But anyhow, that aspect of it never added up for me.
After Valerie Strauss's most recent gaze into Michelle Rhee's navel, I might understand better at least why Rhee thinks closing the achievement gap is a viable idea. If you think middle and upper class white kids are lazy, over-praised and undisciplined veal calves incapable of responding to hard working immigrants and striving poor kids, and you believe that a powerful, fair and objective technocracy will run education, then I guess you would think that the achievement gap is indeed closable.