not sure why you're getting downvoted for this, I had the same experience with my education in the US. high school class of 08, lol. the school never taught a math class past algebra 1. if you finished it, you still needed math credits per year, so they'd just have you retake the same class. seriously. absolutely abysmal. 95% of the math I do now is self taught. from my "education" alone, we never got much past solving basic linear single-variable equations. most of my class graduated barely literate. really, most of my class simply left, myself included - the dropout rate was astonishingly high around 08, and instead of doing the same classes and curriculum for the third time in my senior year, I opted to simply leave, educate myself, and shortly thereafter start my business.

Maybe you were just at a bad school? Quadratic equations are mandatory in Germany even for the lowest level of graduation.

Until my Abitur (12th grade) I learned about equations, stochastics, integrals and derivatives, vector stuff, etc.