I got very shirty and a tad emotional at a parents 'talk' on the sex ed curriculum when my dd was that age. I asked about how they dealt with homosexuality and the reply was "I've never had a child tell me they were worried they were gay". I said that if hey were picking up that it was something they should worry about then no wonder.
I had recently returned from the funeral of one of my own ex pupils - killed himself - had been leading a total double life, gay & out at work in one city, friends & family in home town no idea. He evidently couldn't keep up the deception.
I pointed out to the assembled parents and teacher that statistically about 2 of the children in ths class might be gay, it might be my dd, it might be Jane's ds, how was the school caring for their emotional well being?
IMO It's really not good enough to cater for people's prejudice and embarrassment when there are lives at stake. We teach the facts of evolution while recognising people have religious objections to it, we should teach the facts of differing sexualities in the same unemotional way.
Homosexual attraction is a normal variant, sex has a number of purposes, one of them is to have babies (so penises go into vaginas) but it's also a way for people to show they care about each other which involves a lot of kissing and cuddling and stroking and it doesn't need a penis to go into a vagina for that to happen. It can happen between a man & woman, man & man or woman & woman. It's not rocket science and it's not difficult to explain, it just needs to be done by someone trained and capable. You wouldn't expect a creationist to teach evolution well so why would you expect someone embarrassed about the idea of gay sex to teach human sexuality well?
I think you've taken the right approach OP - but if this is school policy I would urge all parents to challenge it. What if your child is gay? What message about themselves do you want them to be hearing?
A number of years after my school incident a friend of my then dh killed himself because he couldn't come out to his parents - he believed they'd rather have a dead son than a gay son :(
The situation is obviously better than it was - at secondary school all my dcs had friends who were gay or lesbian and out, unheard of in my day - but we need to tackle prejudice where we find it - and schools not talking about gay sex when they will talk about straight sex IS prejudice.