Back in our illustrious past, one-room schools contained several grades and usually one teacher.
My mother and father attended such a one-room school, and mother taught a one room school for several years during the '20's. Many fifth graders helped their fourth, and third grade etc roommates.
In some semi-frontier schools attended primarily by farm kids, a lot of the kids were related, brothers, sisters, and cousins and they were expected by their parents to help teach the younger ones, quietly at school and intensely at home.
The learning of the students reached some pretty high goals.
Might have worked in the old days, but nowadays, we’d just get idiots teaching slightly younger idiots.