I find this hard to believe. I remember hearing it growing up a ton. I can't count how many times but it was used a lot. I saw a kid from my HS beat the crap out of someone who called him that. I know it is a problem in my father-in-laws city up north because there has been complaints about kids calling a AA kid in the school that.
There were just recent stories the last couple years about opposing fans at HS sports games using racial slurs against kids.
I never said the word wasn't used, only that I only heard it a handful of times. I too heard stories of some racial slurs used in HS FB games. A classmate of my daughter (no pics) who is the son of a very good friend, said there was a certain school in CR (not a public school) that was notorious for that.