I’m not sure if “admits” is the right word. I don’t quite buy the learn-nothing Academically Adrift line of research, although I certainly don’t think students come away knowing near everything that’s taught, and if we did know the precise amount learned it would probably be disappointing for a lot of people. I was more emphasizing the ways in which skills that aren’t intended (or necessarily glamorous) can be taught in education because that’s the less obvious pathway.
Ed school is an interesting note to all this. Based on teacher productivity research I do tend to buy that ed school (in particular MA programs) is much more (perhaps almost entirely) signaling, certainly much moreso than other forms of education, i.e. letting already-strong teachers prove themselves rather than making them much better.