Apparently around 15% of highschoolers take calculus. I dunno, I think “significantly less than 50%” has a generally right-ish feeling, sort of like, something that most people don’t do but not like super-esoteric. But it is subjective.

https://www.edweek.org/teaching-learning/calculus-is-the-pea...

It is possible that the majority of students forget it though, I tutored calculus for a bit and it didn’t always seem like their hearts were in it.