Filtered against evil
Far be it for me to bring this up on someone else's post, because I know a number of you will disagree with me. But I fail to see how keeping those under a certain age from learning how to defend themselves against the evils of this place can be at all beneficial. As a singular example, and I know there are many, Hermione has expressed a great deal of interest in learning these things and whilst I have consented to teach her what I can, there are those of you able to teach her other things that I myself cannot, beyond simple physical defences.
I suppose the real question is, why might they be permitted to attend classes offered here, but are restricted from attending the camp? Where does the difference lie?