Comment by human_person

Yes but that’s because you (mostly) stop physically growing once you are out of school. Banded within a year is meaningless for adults, a 25 yr old isn’t that different than a 30 year old but a 5 year old and a 10 year old are distinctly different. They are at different points in their development physically, emotionally and mentally. They socialize differently and have different needs. I’m not saying they can’t interact but there is some value in keeping children together by developmental stage and developmental stage is fairly age specific.