It probably depends a lot on where you are. I mean, a lot of programs are still teaching 'abstinence only', so I think expecting a lesson on homosexuality is a bit much.
I was out sick the week in middle school when this was covered, so I missed a lot of it, but I don't think that was really mentioned.
I skipped the 'health' class and just took an abbreviated version online. Sex ed was barely mentioned, I don't think homosexuality was ever touched on.
It's a good thing I'm ace and don't really need to know this stuff, because now that I think about it I got basically no sex ed in school.