>You'll wind up just knowing the formulas from paying attention in math class, and especially from doing all the homework problems and taking all the math classes your high school offers. To be sure, maybe your high school is deficient in teaching math (mine was). For test prep, then you need some extra math instruction, not test prep.

I don't agree that math classes are enough because teachers do vary, some sucks, some are great, but also at the end of the day they have to teach whole class, not just you, meanwhile maths on youtube runs at your pace