To me, the more interesting story is parents of normal performance kids holding them back a year in school. If you want to get into a top college, better to be 98% percentile a year later than 90% percentile a year earlier.

The difference could be 2x or 5x lifetime earnings depending on things like getting into top college and then Med school or Wall St. But it’s a zero sum game, the families who kept their kids in the normal year/age lose a slot they could otherwise have competed for.

It used to be common to promote top performing kids ahead a year in school because the child would be more engaged and happy. That’s not the thinking anymore.