I think there’s a significant difference between fourth grade and high school level math, especially the more advanced courses. I got the flu in 9th grade and missed a week of trigonometry. I was able to catch up and it wasn’t the end of the world, but it wasn’t trivial, there absolutely was a “catch up” period.
Agreed university is much harder though.
You were fortunate in attending a better school.
I was an air force brat, and so attended many diverse public schools.
I took 2 years of honors physics in high school. College freshman physics blew through that in 2 weeks. And then I was in deep doo-doo.
I am eternally grateful to Prof Ricardo Gomez, who kindly took the time to coach me one on one. I never thanked him for that, one of my many regrets.