We've had some similar situations here at my school involving the talent show, not really with flags though. Some kids I know were gonna sing a version of the Adam Sandlers hannukah song, but they adapted it with names of kids from our school, everyone loved it and it was pretty funny, no one had any objections and all the kids ok'd it beforehand, but the administration said since it mentioned "jews" in a poking fun kind of way, and left out making fun of other religions or something, that they couldnt sing it. dunno if thats relevant but some pretty ridiculous things are going on in high schools lately.