>Was that not offered at your school?

I think it would have been theoretically possible, but obviously logistically difficult as I would have had to skip multiple classes in other fields to attend.

It's also not like I was particularly interested in mathematics at that point in my life. I essentially chose my field of study based on what I had the best grades in. Only during my studies, when the material actually became difficult, I started to be interested and engaged in the subject.

For the schools that offer students the ability to take university-level courses, students aren't "skipping" other classes.

> Only during my studies, when the material actually became difficult, I started to be interested and engaged in the subject.

Many schools solve this by having different difficulty-levels of courses. My school, in the US, had three.

Germany has different levels of schools. I was in the one for highest education, targeting a university degree.

Schools in the US often offer different tracks within the same school but still offer different difficulty levels within them, including university level courses.