*thinks*
I think grade four is when sex ed started in my school. If not then, then grade 5. And I went to a Catholic school. The focus then was "where do babies come from" and stuff like personal space at the start. Pictures, diagrams, models. And some "professional" speaker would come in and explain it to us with all her own props.
In grade 7 we started the religious side of it, being a Catholic school. So, stuff like commitment and love and how that's involved. But, the teacher's also allowed anonymous questions so that kids could ask what they want without feeling embarrassed.
I think that was sufficient. Although I don't think the disease part of it wasn't really mentioned till high school.
I don't think you need to cover sexual positions and techniques, treat it more like biology - so I guess that's why it currently has a bit of a hetero slant. It for the "where do babies come from" question. But, I do think they should discuss disease and safe sex for both straight and gay. But, maybe more in a discussion form. A lot of the pictures and diagrams we were shown were to demonstrate stuff like egg fertilization or what those areas look like on the inside. Drawings of gay sex wouldn't serve the same purpose and would probably be met with snickers. So, discuss it... but I don't think you have to go in depth with it because there isn't so much of a specific knowledge (its more of an awareness) to be gained from knowing exactly how it works.
And at the same time, I think parents should have control over what and when their child is exposed to at school. Have consent forms. In the early years (before we even started having formal sex ed in school), our school decided to invite some people in to perform some play about abduction and rape. We were really young. I think it may have been grade 1 or 2. So, my parents kept me out of that presentation on the basis of I was still young and innocent and believing in magic and Santa Claus and that age I'm always with them anyway. I didn't need quite that dose of reality just yet. I remember going back to school after that and all the rest of my classmates were like traumatized for a week.