I attended Detroit Public Schools and at that time there were “A” and “B” semester classes [[not to be confused with the “Special B” which was learning-challenged); I was in the “A” where the grade finished in January each year. I think it was based on birth date. IIRC, I was the second youngest in my class with a birthdate at the end of March. I wonder how long DPS did it, and whether it was some kind of experiment to see if kids did better with less age variation; I do know that most of my friends from 6-8th grade were the “B” group, who were a little younger.
Also, my grade school [[Crary) was K through 8th, class was split to a couple of different middle schools for 9th, and different high schools for 10-12th grades. Personally think that wasn’t a particularly brilliant idea, kids at that age being separated from their friends at a pretty social developmental period.
I went to Cerveny where I knew no one [[the A/B thing didn’t help), then Cass Tech for a while [[skipping more than I went), ending up at Cooley. Grades 9-12 for me sucked socially.