Whatever.
The sketch has blond hair of two kids. the mural has darker skin, without blond hair. Did the artist change actual students looks, causing the stir maybe? This is suppose to represent actual students, then the artist changes the students. I read an article that said none of the children were white. I could be in error, but I really don't know.
Here is one pic I could find:
The kid with the afro in the concept is now Hispanic rather than African-American. Could the racial slurs be coming from blacks because the final product was changed to Hispanic?
Where's the blond hair on the kid on the bike, and the bike is changed too. The pose of the black/hispanic is changed.
When you change an approved design, maybe it's not the mural that being called racist, but the painter!
I haven't found any quotes of the slurs, have you? The articles make everyone assume the slurs are coming from whites. What if they aren't?
Remember the black tea party guy with the rifle, being called a racist against blacks?