I don't think many researchers and educators are actually claiming that things like adopting the growth mindset will "close the gap" - that would be a spin added by journalists, etc.
I get somewhat when I read about "closing the gap" as a goal of education; it gives the impression that a policy that improves all children is strictly worse than a policy that improves only stupid children by the same amount.
Well, equality is one of the human values. I think the journalists are adding this spin because readers want to read it; because it is a political topic. Saying that one child leaves the school system smarter than the other child makes people think "that's unfair". And being unfair, especially towards children, is a bad thing. So yes, a policy that improves all children is strictly worse at creating a feeling of equality.
(Of course there are other values besides equality, which shouldn't be sacrificed, unless you want to say things like: "No...
Post by fellow LW reader Razib Khan, who many here probably know from the gnxp site or perhaps from his debate with Eliezer.