I have noted this before, and another repetition of this is warranted. There are now many seforim on the subject of chinuch, and the mechabrim are noted in having been or still being recognized as gedolei Yisroel, and others are likutim from well recognized talmidei chachomim. To cite Tanach or Shulchan Aruch without including the manner in which today’s Gedolim explain the relevance to today is dishonest, both intellectually and spiritually.
There is considerable discussion about use of any form of negative physical force. No one says it is never permitted, but it is fairly clear that there are many, many limitations on how, when, and under what circumstances it can be used. A rebbi who delivers a smack out of anger is clearly in violation. Whether a talmid deserved it is not relevant. I interacted once with a menahel whose staff member smacked a talmid multiple times in a manner that was as much a physical assault as it was shaming. The menahel was busy defending this rebbi, until I read verbatim a direct quote from the Brisker Rov ZT”L, wherein he stated that the first potch can sometimes, and under specific conditions be permitted. Anything more than that was an absolute issur “min haTorah”. Needless to say, that menahel claimed to have more knowledge in chinuch than the Brisker Rov. Our call ended there.