When I was in high school, there was a group of guys (of which I was NOT a part) that made busting up mailboxes a summer activity. The owners finally went to purchasing the large rural mailboxes, setting a standard mailbox inside and pouring concrete around the smaller box and mounting them on 6x6 posts. That fixed the problem after a couple of broken wrists happened to some of the football players...
I have seen this, let 'em try and beat that one down.
