>Two-spirit gender is a term used specifically by indigenous communities
and for a person who is not indigenous to use that term can be really
offensive, as it is deeply rooted in culture.

So deeply rooted that it was coined in 1990 to replace the (admittedly offensive) word berdache, which itself was coined by western anthropologists to identify indigenous folks that fell into non-gender conforming roles and who may have been LGBT+. Then, going beyond that, it's a term used to refer to men who, for example, like to cook (a traditionally female role).

So I get it. Folks wanted to throw out the old awful and replace it with new and less bad (although there are folks in the indigenous communities that are unhappy with the term, similar to when latinx was invented). I also get the burning desire to toss aside western cultural ideas as, let's be real, the cultural genocide happening against indigenous folks is a bad time.

That said a lot of this concept feels really really gross. Why do do folks need a term for men that like to cook or women that like to hunt? Why are we still harping on people who do "gender non-conforming" tasks?

Your answer to "why isn't this taught in schools" is, frankly, it's a really community-specific topic. US schools, regionally, teach what needs to be know. Something this culturally specific is way, way under the radar considering all of the other really important stuff that needs to be taught about the indigenous peoples of the US.