Teen pregnancy was very rare in my high school. We had a sex ed class. It lasted a whole semester and we had to take it, and pass it, as a requirement to pass on to the next grade level. If you failed sex ed, you were held back a grade till you did pass it.
It was not an option for us and no one complained about it (at least no one I ever heard). We did have the occasional kid come in with special permission to opt out of the class due to whatever reasoning, but it was a requirement. In exchange for not taking sex ed, they had to take an extra semester of physical education (we had to have 7 to graduate, so they had to have 8).