I believe this is actually a first principles question, to a large extent.
What right does the state have with regards to imposing a particular type of education on children, and also, what obligations does the state have to keep away from controversial belief systems in state provided education.
I don't actually think that's a matter of opinion, as such, it's not about a social consensus about what schools should teach. It's about the role of parents vs the state in children's lives.
It's really important to keep clear in our minds that as soon as we say it is ok, or good, for the state to undermine or contradict parental views that the majority thinks are wrong, we've set a precedent. We should have a very good sense of what the lines are around that and understand that if we don't, it could easily become any set of socially popular beliefs the state sees as it's job to impart.
I think with gender ideology, some people who had been content to allow that the state should use education to indoctrinate children suddenly experienced what this means when you aren't comfortable with the narrative the state is pushing.
I also think the question of belief vs fact is much less helpful here than people might like. In general, in the UK I don't think you'd find many who objected to facts like how biology works, what to expect with puberty, what kinds of birth control are available and whether they work, STIs, and what kinds of things are legal or illegal, rape and sexual assault.
But there are a lot of things that many average people in the UK might think of as facts, that are actually values statements. Things like gender roles in marriage, abortion, sex outside of marriage casual sex, homosexuality, parenting questions, whether sexual fetishes are ok, whether masturbation is ok, whether pornography is ok, whether prostitution is ok. These are all things about which there are many viewpoints, religious and non-religious, that touch on complicated questions about sexual behaviour.
Personally, I have some real doubts about whether schools have any moral right to teach kids about that stuff, and maybe more to the point, I am not at all convinced that most teachers or the people who develop curriculum are capable of addressing these points appropriately in a society that is multicultural and contains a lot of religious and ideological pluralism.
I know it's very much going against the grain or the last decades to say schools should just stay out of those kinds of questions, but I don't see a plausible better solution.