"racial slurs *from the field* heard in the stands"--No, that's not what the article said.

"One Manual High School football player’s parents said she heard racial slurs *coming from the opposing team’s fan section.*"
Either it was pretty quiet in that stadium, there were racist chants from the stands going on (which is tellingly omitted), or that parent has better hearing than a four-legged carnivore, because hearing anything explicit from the opposing stands, short of collective cheering, is practically impossible at that distance.