Chris Rickert:

Lead researcher Sara Goldrick-Rab also said the most recent study — released Monday, of the 2012-13 school year — provides better evidence that the advancements probably come as a result of the program (i.e., they aren’t just a coincidence or a result of other causes).
This is good news for a district that has seen the percentage of low-income students reach 50 percent and now enrolls more students of color than whites.
But it’s not as if these demographic changes were sudden, and the district’s failure to reach low-income, minority students is longstanding.
The achievement gap is clear in state testing data online that goes back to 1996, but it almost certainly existed for many years before that.

Much more on the achievement gap, here.