Most likely that teacher is the wife of the pastor or sister of the mayor or some shit and thus invulnerable

Fuck no. Teachers are in such short supply that they aren't looking for reasons to fire them, just pay them less.

Besides, every state creates their own curriculum. It's possible that's the state's official take on the Native American Genocide. After all, for over 150 years, southern schools have been teaching that the Civil War wasn't about slavery, it was about the states rights to decide their own fates, without interference from the aggressive north. They teach this despite the evidence of their own state constitutions of the era, which all mention the protection of slavery right at the beginning, as well as the Confederate "Declaration of Independence," which puts the blame squarely on Slavery. They've spent 150 years OFFICIALLY teaching an alternative lie.

So that Native America explanation might well be an official government position in your state.

Lol that teacher was pretty much par for the course as far as rural 90's education goes.