I am curious on how school can skip the whole gender identity part considering how central it is in social science and life-science.
i like the idea in saying that boys and girls are the same and that it doesn't impact who they are more than having blonde hair or large feets. However, if you through art/litterature/history you can quickly find out that men and women aren't treated the same. If you to basic biology, you come to some "difference between boys and girls", and may want to discuss which of these difference are biology, and which one are sociology.
Then, it's not like LGBT and intersex individual are novelty, and that kids won't ask question about them (selves). So again something pretty hard to skip. To take medieval history, I don't know how much British kid know about the "acursed king" and the 100 years war, but Edward II being more sexually interested in Lord Despenser than in his wife Isabel the she wolf from France played a big role in these historical sequence of events