I grew up in the era of children being smacked (1940's) I remember my late Mum smacking my bare legs a few times when I was about 7 or 8.. It has never had any lasting effect in my life. But the smack on the legs. did have the desired outcome, if it was something naughty I might have done, after she had given me plenty of warning what she would do if I kept doing something she didn't approve of.
I dare say my late Mum was frazzled and bothered about some things in the war years, and things would get on her nerves, and wear her down, so a child misbehaving would make her lose her cool.
Some police men who walked the streets, were known to give a wayward child a clip around the ears, if they caught them fighting with other children, or trying to steal anything. it usually had the desired effect, as the kids would have been in trouble at home as well for misbehaving in the streets.
I do know a few people who were badly treated at home as kids then, those with Fathers who were heavy drinkers, always at the pub after work, and couldn't cope with noisy and unruly children when they got home, so smacking and other punishments were then dished out to the children, and sometimes the wife.