#1. The word negro in English is not a slur.
#2. The word negro/negra in Spanish (pronounced NAY grow; NAY grah) means black as in the color (un sombrero negro, a black hat; tinta negra, black ink). It is also a term of endearment. It also refers to Black people.
#3. There is no perjorative racial word or slur for Black people in Spanish. There is no n word. To make a racial slur, you’d have to add an adjective, like ugly, evil, etc.
#4. The administrators at this school are illiterate and should be fired.
There certainly is a derogatory term for blacks in Spanish America..the word is mayate.
I told them to stop, or they'd get their asses beat.
By some black dude who DIDN'T think it was "cool".