I spent some of my elementary school years in Florida, where, at the time, we were taught Christianity and songs about Jesus every day in class. We sang hymns and Christian songs every morning and prayed. Of course, now this is seen as biased because there were kids of different religions, such as Jews, in my classes. Where was the consideration for them and the validity of their way of thought?
Teaching one religion as the right one and invalidating others in the process is not the educational prerogative of schools. But teaching comparative systems of thought and belief can be enlightening for any age group.