I was taught consistently what is and isn't acceptable, and I knew there would be consequences if I misbehaved. I parent dd in the same way. I wasn't smacked, and neither is dd, but I will remove her from fun activities, remove toys, tell her off if she is naughty, and do not let her get away with poor behaviour.
As a result dd is well behaved. She knows that we are quiet in the cinema, you sit nicely at the table (without a screen), she is polite and people enjoy her company, she is friendly and helpful at school, she doesn't run riot in the supermarket/shops, she walks nicely by the road. I have repeatedly and consistently showed her the boundaries in different situations and she understands what is expected of her.
I think children are badly behaved now because adults let them do whatever they want, even going against teachers who dare to hope the children might behave in school. I respect dd's teachers and speak positively about them and dd therefore respects them too.
Incase it sounds like I am harsh on dd, I will point out that i very rarely shout, I have never been violent towards her, and I am very warm and cuddly with her. I just don't accept bad behaviour.