I really don't think references to religion are a problem. My AP English class read parts of the Bible itself - because it has significant literary and historic importance even if you don't view it as a religious text. This is in a secular public school in a very liberal state only recently. Nobody objected, because if you start going down that road, you will have to throw out pretty much everything written before 1800.
Many schools do start down that road. Having the Bible in your classroom even for purely non religious reasons has gotten people in trouble before and many schools just don't want the hassle so they outright ban it.
It's always been odd to me that freedom of religion is so frequently interpreted as denial of its existence. At some point, the extent to which public society goes to avoid acknowledging it becomes kind of silly. And, of course, when taken too far, it actually infringes on true freedom for those who practice.
Indeed, there's a world of difference between reading religious texts or listening to material that may make reference to religious matter, for the purpose of comprehension or understanding historical context etc, and it being used for proselytism.
