Earlier quoted context omitted.
I think the big difference here is that it doesn't really matter if someone isn't athletic. A school can have 10 kids for an amazing basketball team and 990 that are terrible at basketball and it doesn't affect anything, but if you have 10 geniuses and 990 kids that can't read then it's a huge negative for society
Given the test-driven nature of modern education in the US, having 1000 kids that can just read at grade level is better than having 985 kids at grade level, 5 below, and 10 above. Any resources spent on the latter would be better spent on the 5 that are below grade level.
Personal side note; I’ve tended to find that exceptional people are more productive with the resources given. So I find it hard to believe the inverse would also be true.