I am in my 60's and so was in school when teachers were allowed to administer physical punishment. While I agree that some teachers went too far, in my school, the cane was only ever administered in front of the whole school, so there was no chance of it going too far, and showed all of us what we would happen if we misbehaved badly enough, making sure that the vast majority of kids behaved themselves.
These days, as some posters have said, kids know that there is no real punishment, and nothing that a teacher can do to make them behave, so if they're that type of kid, then they simply do as they like, and get away with it. I'm not a great believer in physical punishment, because too many people have taken their own frustrations out on their children, and have gone too far, but I do think that some form of punishment is needed to show children that there are limits, and the punishments given today are simply not harsh enough to work on stronger willed kids.
I have also observed over my life time, that the end of physical punishment in schools, signalled the beginning of the extremely poor, and out of control behaviour, that we see in our youngsters today.
People say that children should never be afraid, and yet isn't fear the very basis of our legal system, as most of us are AFRAID of being sent to jail, and that's what stops us breaking the law, or killing each other. However, yet again the 'do gooders' became involved in the prisons over more recent years, and now prisons don't act as the deterrent that they used to do, which is clear by the fact that they're all over crowded, and we actually need to build more of them.
I don't know what the answer actually is, but I do think that behind it all, there needs to be something that we fear, otherwise, what deterrent is there?