The old-fashioned way, in my family's case. We're working class but raised with high expectations. Taught what you might call posture and deportment from as soon as we could walk ... and often hit for slouching, 'lurking', mumbling or being 'rude'. Rudeness included child-like errors such as commenting on someone's appearance, asking intrusive questions or taking food when not invited to help ourselves.
We had perfect table manners. Parents often took us to restaurants; other diners would compliment them on our fabulous behaviour. We had dinner round the table every evening. Conversation was mandatory and would cover everything from "How was your day" to "What do you think about Premier Khrushchev's promises on nuclear de-escalation?"
When we didn't know something, we were required to look it up - at the library if no suitable source was available at home, though it usually was. We all joined debating clubs (schools used to do it as a matter of course).
We travelled around Europe every summer in a camper van. We learned something of the languages as we went. Weekends were forced marches over all the mountains of England and Wales, often with actual rock climbing. We learned to identify plants, wildlife, basic tracking, etc. We learned to swim very young.
I often say I wasn't brought up, I was trained! Much of the way my Dad did this was brutal. We are not without emotional scars, very deep in my case. BUT they did a fantastic job of giving us an all-round education, social & physical as well as academic.
Pretty sure this can be achieved without the rages, beatings and insults.