So a teacher was sacked simply for asking why a student chose to wear a hijab? If so, that's absolutely ridiculous. It would also be ridiculous to sack her for refusing the student entry (unless, of course, it was done maliciously), I think the intent of the teacher is what is important here. If she meant to act in inappropriately, then she should be removed. But if, for example, she was unaware of the rules, then the answer would simply be to politely educate her and chastise the principal for not properly orientating the teachers to their school.

Isn't that was good hospitality is all about? If your guest makes an error out of ignorance, do you assault him?