RB, C”V, no absolutely not, but that wasn’t the question presented, the question was about the Rebbe. In some instances depending on the age of the child a parent might find that a potch on the behind serves a purpose, like a child running into the street, where a discussion about the danger of doing so will have no effect. Again depending on the age of the child and circumstances.
And, RB, a potch on the behind for a dangerous circumstance is not equivalent to smacking a child which is only done in anger. A rule for parents is to take two deep breaths before reacting. If you try to calm down before reacting your reaction would be more logical and not physical. You would either remove yourself to calm down or tell your child to walk away till you calm down.
As far as the Rebbe is concerned, there was a great Rebbe in that yeshiva which both my boys had I think in the 5th grade I am not sure. The Rebbe I believe is still there. At any rate, whenever the boys did something wrong and needed discipline he would tell them “remind me later that I owe you a potch”. That was it. He got his message across without touching anyone. And this is the same Rebbe that played basketball, dodge ball and arranged trips for them. Did this Rebbe love his talmidim? Yes, every one of the them. And that’s why he is a Rebbe.