Well when you suffer pain for doing something, it becomes instinct that it's something you shouldn't do. When you're told you're doing something you shouldn't be, well most kids don't give a damn or it goes into memory. Memories are often forgot.
I shall say I've experienced being beaten with a metal coat hanger. Which is certainly going too far. I now lack any social skills whatsoever (I'm serious on that note, when I'm on the phone to my aunt or something I don't know how to start a conversation). There's also my cousin who gets beaten with a wooden stick.
I'd say that to some extent physical punishment is acceptable. Like a smack in the face or something. Not beating children with solid objects. I mean people these days (I don't know if this is the case for everyone) are lacking discipline. Chatter in class, chewing gum under tables, refusing to clean your room, underage smoking...
I never chat in class or talk back to the teacher because I distinctly remember when I was sitting in my mum's lap crying about something and my dad was lecturing my brothers I interrupted him about something and then a lot of pain then my mother holding me. I shall never interrupt someone again.
Of course they think I'm mature enough to actually understand their lectures now and don't beat me anymore.
Conclusion
Until the child is mature enough to understand why the parent is lecturing them, I find that physical punishment to some extent is acceptable.
