This is the detail which needs to be added to almost all mainstream coverage of education stats — every year you'll see some hand-wringing about U.S. students falling behind internationally and the authors never mention that the effect is much weaker once you correct for the fact the U.S. has a much wider range of students taking most tests. Usually almost all of these metrics come back to the root cause of economic disparities along the spectrum from hard poverty to not being able to afford tutors and SAT prep courses.
(This is also why the cool curriculum ideas or charter school concepts we hear about never go anywhere: the TED Talk sounds great but inevitably once it scales up it turns out that the effects were due to some sort of selection bias (quite possibly unintentional) or simply lucky small sample sizes which peters out at larger scale)
(This is also why the cool curriculum ideas or charter school concepts we hear about never go anywhere: the TED Talk sounds great but inevitably once it scales up it turns out that the effects were due to some sort of selection bias (quite possibly unintentional) or simply lucky small sample sizes which peters out at larger scale)