My first sex ed classes were in my final year of primary school, almost 20 years ago now. I'd already talked the birds and the bees with my parents, as had a lot of my friends, so most of us knew what sex was but still didn't really understand all the mechanics of it, unless any of them had already started watching porn. I knew I was more interested in guys than girls, but didn't really understand what it meant until I went through several spells of unrequited love that began in my adolescence. We had further sex ed classes in my first year of secondary school, again taught from a purely biological perspective. Beyond that, it was hardly touched upon in PSHE (Personal, Social, Health, and Economic Education). I remember drugs and alcohol being covered a lot, and politics 101. Around the time of my GCSEs (High School Freshman and Sophomore) I remember the teacher mentioning vaginal and anal sex and a few students giggling, and homosexuality was very lightly touched upon, but only within the context of the AIDS crisis.
I don't know of any lesbians or trans people that were in my year at school. I was one of about half a dozen gay guys in the year, and was at best friendly acquaintances with them. None of them were out but everyone knew, as between them they had all the main stereotypes covered, and they've all since come out as adults. I wasn't particularly interested in being friends with them anyway as they all had exclusively female friendship groups and had stereotypically girly interests and personality traits, whereas all my friends were guys, who I was out to.
People made immature jokes around years 7 and 8 (6th and 7th Grade), that weren't meant to be malicious I don't think, often aimed at the other guys because they were more feminine, and not particularly athletically-inclined (I'm not much of a natural athlete myself; fairly good runner and swimmer, but zero technical skill in football, rugby, cricket, or tennis; but I at least always gave it my full effort. One of these guys got away with never doing PE; I think the teachers just 'gave up' on him). By the time of Sixth Form (High School Junior and Senior) pretty much everyone was cool with it. I did feel isolated in the sense that I was the only 'straight-acting' gay guy, and it doesn't help that the majority of gay icons and celebrities are themselves camp as well. This has continued since then as even at uni it was still predominantly camp gay guys on my course. I basically went back into the closet during my Master's degree and only told my closest friend. To this day, all my friends are straight guys, and it's only online, mostly because of COVID, that I've been able to interact with other gay guys that I share things in common with besides the obvious.