Earlier quoted context omitted.
Because taking geometry in 8th vs 9th vs 10th grade doesn’t really matter. And given we are otherwise doing just fine, I think stagnation is far more likely to come from somewhere else.
I’m sorry, could you give some context to non-Americans? What does “taking geometry” mean? My school had geometry as a subject in grades 7-11 (with 11 being the final year), were you expected to pack it all in one? How does that work?
Given typical HS math curriculum (algebra/geometry up to calculus) being able to offer geometry early gives enough time to offer calculus; otherwise a school could teach it late and it won't matter because math education stops early anyway.
Also connotes to a degree college-track vs non college-track students, again due to the highest math a HS offers. It is extremely desirable to take calculus in HS to prepare for college, but if most students don't go to college, no need to take/offer calculus, no need to start the math sequence early, etc.
I went to HS in the US and I remember a split in the math curriculum starting in 10th grade (I didn't go to my HS in 9th grade so I can't say). The vast majority of kids planning on college took a combined algebra 2/trigonometry class in 10th grade; the other kids took either algebra 1, geometry, or algebra 2 (without the trig) depending on previous courses.
So the comment "taking geometry in 8th vs 9th vs 10th grade" would mean something like comparing schools for numbers of college-track students and funding (8th grade great - implies a HS with a large body of students going to college, well funded in order to offer variety of classes; 10th grade not good - implies a HS with a small body of students going to college; not well funded, math stops before calculus, etc.)