I think there's a happy medium between 100% approval and corporal punishment. I never cared about grades, but could always tell when my kids weren't giving their studies their best effort. I could disapprove of that while still making it crystal clear that I loved and supported them, 100%. I wasn't judging them on their failures - maybe on not trying hard enough to have more of them. ;)

Unfortunately, in some places, teachers CAN dish out corporal punishment. I think parents have to consent - at least in my state. I never did! I think I wrote in things like, "Don't you DARE!" whenever the form asked the question. But some parents are all for it.