Earlier quoted context omitted.
Countries often scrub their history books of things they're not proud of. I grew up in the US and not once was the 1921 Tulsa massacre covered in school.
I grew up in NYC and definitely learned about Tulsa.
My AP US History introduced the civil war section by saying despite his personal beliefs, he was teaching us to pass the exam and any discussion about the war being over slavery and not state's rights was a waste of class time as that would not get us a four or five on the test.