^This.His shirt was inappropriate. I remember a while back I wore a shirt with a gun on it in school and everyone warned be it wasn't allowed by the rules, neither was boodly/gore photographs. I didn't get in trouble though because there wasn't people so overly sensitized like there is today.
I bet if anyone wore a "raising the flag over iwa jima" or "washingtons crossing" picture shirt the school wouldn't care.