Are these results broken down by race? If not, we could be seeing static or even improving results, hidden by the shifting demographics of the USA.

When you examine Goodschools data for a given area, there is a very high correlation between the White/Asian student population and the overall performance of the school, including for Black/Hispanic children.

Additionally, how much have politics impacted results for the worst performing students? Anecdotally, its a lot harder to expel or discipline certain consistently disruptive students now.