Your misinterpreting my post. It isn't "her religion" that's the issue - she could be an atheist and say "oh my God" seven thousand times a day herself outside of school. But in school, she has to make sure that the students are not offended and complaining to their parents when they get home that they were upset by this kid. Those parents are complaining to her, and possibly going over her head to the Principal and who knows who else. She is trying to provide a safe learning environment (i.e. keep the peace) for the greatest number of students. I can guarantee you that at least some of them are very religious and will be upset by "oh my God" (taking the Lord's name in vain). Being a teacher is very, very hard these days, OP should be mindful of that and encourage her kid to follow the class rules without making a huge fuss. Even if that family thinks it's silly, it will be an exercise in self-control and caring about others for him.