You might be surprised by my answer but the public schools have treated Christianity like this for....well, maybe since the beginning. For example: many Christian holidays are built into schools breaks, such as Christmas and Good Friday. And I remember back in the day having non-meat meals on Fridays to accommodate Catholics.
(To be clear: I do not think the strictest form of Islam is conducive to American values at all, and I have a lot to say about Islam as a religion, as a Christian. BUT that's not what this thread is about; it's about the treatment of religion in public schools....)