...

Maybe "evened out" is actually code for "given up" or "become compliant."
I have to wonder just what that third grade selection process is
actually selecting for-- because most HG+ kids simply can't
take being that compliant with things that far from their proximal zones for years on end. Not without figuring out some coping on their own-- and most of that coping is going to be about on par with what one might expect 4-8yo children to come up with. Defiance, refusal, daydreaming, clowning, etc. all offer some rewards in a pretty unrewarding environment, after all. Sure, as an adult I see how those things are counterproductive or even maladaptive in the long run-- but for a 6yo, they offer immediate rewards, not the least of which is an alternative to doing mind-numbing things like an automaton.