I'm not sure how that holds legally, but it seems logical.
Having said that, I'd prefer not to see the flag of any country desecrated. And, having said that, I can't help but remember the thousands marching in support of illegal immigration in LA waving the Mexican flag ... that offended me!
There’s more to the story, of course. The school is 1/3 Hispanic, and there is a lot of gang activity, even the colors of shoelaces can start something. The teacher asked the kid to put the flag away, he wouldn’t, so the teacher took it from him until after class. Yes, he put it in the nearest thing to him, an empty garbage can, but the flag wasn’t soiled or desecrated. The teacher was trying to prevent a turf war before it started, now he’s being sued by the ACLU.