No. My take is that test scores are a lousy measure of education. Maybe students are indeed learning less, and that would be worrying, but while we measure that using test score we simply cannot control for test taking ability.

what would be a better repeatable measure of education?

I am not a teacher, nor even an expert in the pedagogical sciences, as a layperson I can point out what looks wrong, but I need not know what is better.

Maybe asking teachers is better. Maybe a robust metric across generations and across population simply does not exist, and cannot exist, and we just have to accept that we cannot compare the education of kids in America today with the education of kids in Guatemala a decade ago.