'learning to listen, take turns, verbalise your reasoning, agree on what you are going to feedback to the teacher, talk to children with whom you never play, interact with children who have a different first language'
All done in preschool at 4, kindergarten at 5 -- i.e. in the years when hardly any formal teaching took place. They did lots of listening through show and tell, as well as asking questions, verbalising of reasoning through group science and pre-maths activities that were hands-on and involved demonstrating to the group, receiving suggestions from the group, forming group conclusions, teacher asking questions to the group. Above all, they did it through educational play, which was their main activity in those years. The issue of talking to children with whom they never played didn't come up as the matter of who played with whom was rotated and what stations they played at was also monitored and rotated. Children learning English as a second language (mostly Spanish and Polish speakers, about a quarter of each class) improved their language skills through almost constant interaction and exchange of ideas with the English speakers as well as with the teacher and aide.
As well as that there was plenty of modelling of what good school behaviour looked like, inclusiveness and friendliness to all included, plus acceptable practices in dispute resolution. By the time they got to first grade they had had about two years of brainwashing in good school behaviour and classroom etiquette (raise you hand to speak, etc.) Throughout their years there, their classroom seating arrangements were changed about every four weeks. The two classes in each year group were remixed every year. There was no visible ability grouping. The children were never given the impression that there was any superior or inferior group in the class, no official recognition given to their own observation of who was 'the best at maths', 'the best at art', etc.
It is a pity to mix up formal teaching with the equally important social and emotional education that needs to take place first if children are going to function successfully and supportively as part of a group in a learning environment. In the DCs' school being supportive of your classmates' learning once formal teaching got under way meant working quietly and independently when solo work was done, and working co-operatively and steadily in groups of usually four children on the few occasions when group work was assigned. It meant moving through the classroom in an orderly fashion and keeping your hands to yourself, and above all it meant being kind to the other children. This was really drummed into them.
If a child finished their solo work early they had their 'never done work' folder stocked with a variety of worksheets, puzzles, paragraph prompts, maths puzzles and questions in their desk to tackle and hand in when the class period was over. The idea was to contribute to a positive learning environment by allowing the teacher to teach, to hear everyone's reading individually every day and to go over everyone's arithmetic every day (so the weaker students got help from a professional and not a peer), and to allow the children who tended to finish assigned work quickly to move ahead seamlessly and without a prompt from the teacher to something challenging and interesting (so no need for the horribly divisive practice of visible ability grouping in the classroom) -- so you cleaned up your own mess and took care of your supplies, you worked quietly and you never sat around twiddling your thumbs, you didn't disrupt, you didn't bother the other children, you stayed on task in group activities and you practiced dispute resolution if someone wasn't co-operating.
At the same time, there was a lot of oral work, with show and tell, children chosen to explain something to the class, children asked to contribute their group conclusion or their group question after a project, suggestions and comments about a story elicited by the teacher at circle time, and input requested from every student when they had their daily chat about the weather, the season and their journals, and at prayer time when they could ask the class to pray for something that was on their minds. This practice in particular continued right through until they graduated at 14 and it helped them develop a sense of compassion. Old schoolish perhaps...
Group work became more frequent as they got older, once they had developed a sense of personal responsibility for their work -- a necessary precursor to successful group learning imo. The social skills and sense of team loyalty needed for successful group work that is a learning experience for all tend to develop later than age 4-7. A sense of team allegiance and a willingness to contribute to a team is a mindset you are more likely to find in ages 7+ if children have a solid foundation of a sense of personal responsibility and a sense of all being equally learners.