Health Class! That's what it was!
I had Health Class in 7th grade where we taught general health things including "sexual health"/education. But mostly only the basics. In 10th grade I had a more hard-core sexual education class as a unit in Boys' PhyEd.
I was in 10th grade 16 years ago. I've no idea how sexual education is treated these days but I can't assume it's gotten more restrictive. I do, however, live in Kansas where Creationism has seriously been considered being taught in schools and in much of the state you can't buy alcohol on Sunday, so.