About twenty-five years ago a rebbe in a NY area yeshiva lost his temper and ran a child’s head into the blackboard. The child suffered a brain hemorrhage and died the next day. I knew one of the area social workers who was trying to get some sort of action going against abuse by teachers. The excuse for not firing abusive rebbbeim? Usually, the rebbe has a family to support and needs a parnassah. So for this he can hit students.
There are three good practical reasons for not allowing hitting.
A. One can never be sure that physical harm will not be done, or that the rebbe has enough self-control to limit his actions.
B. If the rebbe needs to hit in order to maintain control, he doesn’t know how to teach and shouldn’t be in a classroom.
C. Abuse of any sort is a major factor in kids going off the derech, especially if the teacher is abusive and the school/parents don’t protect him.
HItting one’s own child is also iffy – if you do it you have to do it right, and know when. Violence is no substitute for seichel, and just because your parent or rebbe hit you, doesn’t mean it’s a good idea now.
BTW, slapping someone in the face is NEVER allowed. It’s being m’vazeh the tzelem Elokim. Remember that if you cause someone’s face to change color that it’s the equivalent of murder.