> those not sequestered in wealthy enclaves notwithstanding
This seems to speak against the existence of a cap.
> As I understand, for myriad reasons, there is no failing kids anymore.
It's not clear to me whether this is true or whether it relates to high school graduation rates. Unfortunately, The Economist article has no analysis of why students don't graduate, whether they are forced out or simply drop out voluntarily, for whatever reason. The article says, "might not have made the grade," which is weasel wording.
I would put any data from 2020-2022 in its own special category due to the pandemic. The most severe drop in SAT scores was indeed during that period.
There's some irony here, though, because The Economist says, "The trend towards weakening standards can be blamed in part on No Child Left Behind, an education-reform law passed in 2002," but that was the policy of Republican George W. Bush (who actually introduced the phrase "the soft bigotry of low expecations").
> grades have little correlation with performance
Citation needed.
This claim is different from the claim of grade inflation.
> Every kid is legally mandated to have access to a potentially expensive Individual Education Plan
Every disabled kid
> no extra money is given to the schools to provide this
That's obviously a problem, but it would seem the obvious solution to unfunded mandates is to, you know, fund the mandates.