This doesn't make a lot of sense: classrooms are full of other children, who socialize with each other. Classrooms empty into lunchrooms and schoolyards, which are not segregated by year.
> Classrooms empty into lunchrooms and schoolyards, which are not segregated by year.
In my experience, in elementary school our class had assigned tables for lunch and a specific time when we had the playground and blacktop. YMMV. But at any rate a half hour in the cafeteria and a half hour in the yard aren't the best places a child could learn to interact with other children; the characteristics of these activities are constrained by the form of the institution.
My schools (all of them) had open seating and free-for-alls in their open areas; at my high school, they didn’t even bother trying to keep us inside the grounds (which meant that we could, and did, go socialize with the neighborhood.) This is in a school system that contains roughly a million students, and (AFAIK) didn’t impose significant differences between individual schools.
I can’t imagine assigned seating working very well, except for at a very small school in a small district. Yours might not be a representative case.