If I missed a year of fifth grade in 2020, I have had 5 years to recover any lost progress and should do better in 10th grade than the kids that just missed a year. Especially when you consider that many of the topics being tested against are not even introduced until after 5th grade. Sure you might miss out on some arithmetic, but you have had half a decade to correct and your trigonometry scores should be better than students that missed out on trigonometry the same year.

I think the pandemic had some effect on the current cohort of 15 year olds, but it should not be as large of an effect as the students who were 15 in 2020.

If I missed a week of math class at age ten would it have the same effect on a test given when I was 15 as if I had missed a week of math class just before the test? Your position seems to be that missing math class at any point in your schooling is a permanent unrecoverable setback