In theory? Force them to either get rid of the religious iconography or include representations of other faiths, stop preaching in class, teach actual science in science class...
In practice, the government and administrators will bleat and wave their arms and scream "persecution!" until the problem goes away. Which it will. No matter the damages they end up having to pay to the family, they aren't going to let a little thing like other people's rights get in the way of their ideology.