Comparing to this Gallup poll of adult Gen Zers (18-25 year olds):
High schoolers: 26% LGBTQ; 12% bisexual, 11% questioning/other, 3% gay/lesbian
Gen Z adults: 21% LGBTQ; 15% bisexual, 3% questioning/other, 4.5% gay/lesbian
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They also found that, among all high schoolers that have had a sexual experience, 1 in 5 have had a same-sex experience (20%; 14% with both genders, 6% only with the same gender). Assuming that number will probably go up for them as they have more experiences.
And I feel like that's pretty interesting to note, because there's an annoying stereotype going around that most bi people, especially bi women, will only fall into opposite-sex experiences because they're a 1 or 2 the Kinsey scale. Obviously those people are valid too, but I don't think they represent the majority of bi people, and there's often some invalidation coming when people say that. I saw this study posted on Reddit, and people were like "it's probably just 99% straight kids looking for attention and trying to feel unique." That just isn't true.
Some anecdotal talk: I go to a progressive-ish college, and from my uni experience so far, I'd say like 1/4 of the people I became friends with at random (mostly guys) have ending up telling me they're LGBT in some form or another. And yeah, most of those people are bi.
Most bi people I know don't seem to have a preference at all, actually, a good chunk of them (including me) seem to have a preference for the same gender. I think I know one bi guy that says he only likes very feminine guys and enbies, so he's only been with girls so far. But other than that, all the bi people I know have either been with both main genders or only the same-gender! I had a talk with my straight friends actually, a lot of them said they have maybe a 5% same-sex attraction, but wouldn't identify as anything but straight because they can't see themselves with the same gender. I mean they could if they wanted to, that's probably an even much larger chunk of the population, but I'm assuming most people like that will keep identifying as straight.
I was in high school in the late 90s. Granted, this was a in conservative Midwestern US suburb so YMMV… but in my high school of -2,000 students not a single one was openly LGBTQ (or at least they were extremely low key about it). There was one teacher who didn’t explicitly say it but did everything but spell it out for you. Things really have changed since then.