What I really like is his conclusion:
At lower levels I would say that is very much true. And the tension between the stated goals and the actual goals often cause problems that are difficult to address because you cannot admit to the root cause of the problem. It is similar to the problem where educator are always starting "Its for the children". Well if society was "all about the children", parent-teacher nights would be swamped.So why do we insist on getting teens up early, if that hinders learning? For the same reason we test and rank students so often, even though that also hinders learning. School isn’t about learning the content of classes – its more about socializing humans to accept industrial workplace norms and practices.
In higher education, signaling is probably as important an issue as learning. I have gone over this a number of times, one of the more entertaining times I brought it up was here.