“They pull out Mexican flags, and push them in our faces.”
Do you have some inside knowledge that proves that the student who placed the Mexican flag at the school is an illegal alien or not a US citizen?
Doesn't really matter, actually. The Mexican flag shouldn't be flown in a US school unless it flies BELOW the US flag. I'd have removed it, and enjoyed my 3 days off. Of course, back when I was in school, nobody would have thought of doing something as offensive as putting a Mexican flag on display.