"It has a fine long history. All the way back in June 2009, we can find Arnie Duncan talking about the five percent in his address to the conference of the National Alliance of Public Charter Schools. The address, "Turning Around the Bottom Five Percent," and it features the rhetorical sleight-of-hand that usually accompanies discussion of the five percent.
"Or the other big question mark in this whole system-- the state will take those bottom five percent schools and do.... what? Turn them around and fix them? Is there any indication that the states or the privateers that they invariably hire to do the work-- do any of them know the secret sauce for turning schools around? If they don't, then what is the point of this exercise? If they do, why did we decide that only the bottom five percent would get the benefit of this miraculous brew of fairy dust and unicorn pee?
Any time you see "bottom five percent" crop up, beware. It's one more time that reformsters are just making stuff up but trusting you'll believe them because, look, numbers!"