In theory, one can say that spanking could be done under certain conditions, including the parent not acting on their anger but for sole benefit of the child (this is halakha for any tochecha)
In practice, people who are capable of self-control to fulfill those conditions, probably can find other ways of influencing a child in 99% of the cases.
Thus, with this Bayesian prior, if you see someone spanking, there is 99% chance that this is wrong and should be stopped.
This is even more true with the Rebbes than parents or trained teachers. Not just my opinion. I once asked a Rav about children behavior at school. He said that, according to his observation, it is evident where the problem is, if a child (or more often, many children) behaves in one class, and do not – in another.
So, you can apply the same test here: if you think child X deserve a patch, is there an agreement on that between all parents and teachers? Given them all a call. It will help anyway (one of the methods of dealing with anger is to delay the process).