You never beat a kid. Never.
Discipline is important, yes. But corporal punishment is nothing but counter-productive.
You can read the psychological literature on "operant conditioning, habit forming, reinforcement learning" and go from there.
Or you can just see it as the abuse of power it is.
Because wether you are a parent or teacher, the kid is utterly dependent of you.
It depends on you for food, shelter, protection, learning, a future.
It is also utterly powerless to do anything on its own, except maybe to piss you off a bit. Physically, it has nothing on you, either.
So it needs to trust in you to put up boundaries, teach it how to behave and protect it when it strays over the limits, and however hard that may be, YOU are the adult, YOU have to be responsible.
To abuse that trust is the worst you can do to a kid.
To make it clear:
I am in NO WAY anti-authoritarian, far from it.
Beating a kid is out of the question however, for parents and teachers or anyone.
::emp::