OOH! OOH! I know! We could not teach ANY religion in public school classrooms! That's it! That way, we don't have to worry about some religions getting taught and others left in the cold. You are right that we can't teach them ALL, so why not refrain from...gosh what's the best way to put it...refrain from making a law respecting an establishment of religion! That way you'd have your government, like the "state", over here and your religion, like the "church", over here and they'd be...I don't know, like seperate. I think that's probably the only way to be fair and equal under the law.
I think you're confusing teaching religion with teaching ABOUT religion.
Schools have a responsibility to teach children about the world, and you can't do that while leaving something as important to history and culture as religion.
However, it belongs in philosophy and history classes. (Again, ABOUT religion.)