All children of the same age aren't equally emotionally/socially developed. By your own argument we shouldn't be bucketing by age but by emotional/social develo

All children of the same age aren't equally emotionally/socially developed. By your own argument we shouldn't be bucketing by age but by emotional/social development. Bucketing kids who are emotionally/socially more mature than their peers into the same cohort is is a disservice to both groups. Take any vertical you want and you'll find the same argument. The progression by age seems to be approximately correct when you average development across all verticals across an age group when you look at it from a high level, but once you zoom in it's an absolute mess.