I was genuinely surprised to learn this in high school (for me, 2017-2021 or so) - not because it's not a notable event in US history but because I was surprised my history teacher was allowed to teach it.
Many history text textbooks downplay slavery to such an extent that most high-school graduates think the Civil War was about “states rights” when it was really about several states committing treason in defense of slavery.
The genocide and ongoing mistreatment of Native Peoples is barely covered.
In some states, teachers are required to sign documents saying they don’t support the BDS (boycott, divest, sanction) movement against Israel.
But please, do go on about free speech.
1: Only 8% of students understand that slavery was the cause of the Civil War.
2: Here is a book that destroys the myth of the Alamo, and points out that the white people in Texas went to war twice to keep the institution of slavery.
3: There are lots results for problems with the way native history is taught in the US. I grabbed an interesting read as an example. As further evidence, until a few years ago, the Washington NFL team used a racist slur as its name
1: https://www.usnews.com/news/education-news/articles/2018-02-...
2: https://www.penguinrandomhouse.com/books/623832/forget-the-a...