Isn’t this driven by grouping children by age? I.e. a kid born 6 months before the school year will have a developmental advantage over the other kids in the same group. If so, the title could be changed to: using age to group children creates unfair differences in competencies.
Yep. You see the same effect with kids who aren’t performing well in school. It’s mostly because they’re 11 months younger than their peers
Yup, and this is not new information. i’ve seen studies about this effect for at least a decade, probably more like 2 but time flies now
How I read the article it’s pretty much exactly that. I suspect the challenge with your suggestion is that playing sports pretty much requires grouping children in some way, and unless you have multiple seasons of the same sport within the same year and quite a few children to choose from, the smallest natural division would usually be age, by year.