To update on the sibling comment I posted, after reading this study, I think it is pretty flawed. They indeed have an interesting population they have chosen to

To update on the sibling comment I posted, after reading this study, I think it is pretty flawed. They indeed have an interesting population they have chosen to test, but to claim that they are the 1% top performers is incredibly misleading. The other 99% of their peers were never tested in the same fashion, which leads to obvious sampling and bias problems. This special population was treated differently from the other 99% of students from the very start of the study, so there is no surprise that new internal dynamics will appear among them, simply by virtue of being observed and treated as a separate group. To start testing the validity of the claims in this paper a study needs to be performed where the strength of effect has to be considered, when comparing a similar one-percenter group and a larger ten-percenter group. My prediction is that the strength of effect would show only negligible differences, confirming my hunch that the special treatment[1] is what created the new subdivision in this new group. More reading material on this topic would certainly be interesting, if you have anything in mind. [1]: The special treatment in this paper being telling a kid "you are only a 7th grader, but you are as smart as a high schooler".