Well, the author is assuming that high grades are perfectly correlated with learning and retention - I'm not so sure that's the case. I understand why we need

Well, the author is assuming that high grades are perfectly correlated with learning and retention - I'm not so sure that's the case. I understand why we need grades as a motivator and a metric, but they're only part of the story. I got a decent grade when I took undergraduate calculus 25 years ago, but I didn't really learn or retain much - at best, it was in my mind that if I ever needed to figure a rate of change, then I would probably have to go look up how to do derivatives. On the other hand, I recently came across my old undergraduate calculus textbook and started re-reading it just for the heck of it, working all the problems, taking as long as I damned well pleased on each one. And now I feel like I _am_ actually learning and retaining, partly because I'm not rushing to meet an artificial deadline.