Also, can someone explain to me how maths is taught in USA? Because it's very different from the English system, it seems.

Well In my high school you first learn Algebra in 9th Geometry 10th Trigonometry 11th and pre calc 12th. (or if your like me Algebra in 8th, Geometry in 9th, Trigonometry 10th, Pre calc 11th, and I think calc 12th.