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Because they don't understand that teachers and people in authority at school cannot lead students in prayer is not an attack on their religion. They don't know what persecution is.

None that I know of though some school officials don't understand that the Bible can be taught as literature as long as the teacher doesn't give it a theological spin to it.

They can talk about the foundation and history of the religions but they can't make their students practice it.
Freshman year we studied World History and spent a lot of time on the major world religions: Confucianism, Buddhism, Hinduism, Christianity, Judaism, Islam and a little Taoism. So, yes, you are allowed to talk about Christianity in public schools, teachers just aren't allowed to indoctrinate their students.
Some people get a little too overboard and think they can't even say the names of Christian holidays aloud, but they really can. Nothing will happen if you do, maybe someone will be too sensitive and say "Not everyone celebrates that!" but whatever.