The school will argue that, maybe lose, and continue doing what they were doing anyway. My eldest daughter's boyfriend is from Shreveport, and he says even if found to be in the wrong all that will happen is the teacher will be told not to do it again officially, and unofficially they will ignore it while she continues. This sort of thing is standard around there and 99% of kids and parents would never consider questioning it.
This is the bible belt of America, most people there grow up believing in Genesis, and think the Theory of Evolution belongs in the fiction section of the library (if it hasn't been burnt already).
Best idea is to build a wall around them and leave them to it, eventually they will start killing each other like all good Christians.