Humans are social animals, and learn in mixed-age groups, when they learn naturally. A family can create that natural learning environment, or can fail to create it. :-/ Being around other people, though, IF AND WHEN a child wants to learn and is encouraged by parents to learn how to be considerate and sociable, can be a good place to learn "manners"—ways to behave politely.
In school, children are still social animals with the need to identify who might help them, and what their role is within the social structure. The social structure being unnaturally 20+ kids the same age, they figure out who are the leaders and the "young" and they act in accordance with their instincts in an unnatural setting. More adults to—teens, and young adults, and middle-aged, and elderly, behaving in natural real-world ways. TV is better for that than school is. Ideally, a rich unschooled life *IN* the real world is better than either.
photo by Julie D
I can't find where I wrote that, up there, but three people shared it in 2012,
and I still think it's true. —Sandra