It's a good idea; there's a lot that can be learned from religions, and many people are sorely uneducated in religious matters. As most social studies classes include a bit of religion in them, I think a religious class should be an optional Grade 11/12 course (there would be a lot of fighting over whether or not a school could put a full religious course in the required curriculum...).
If nothing else, religion is interesting. I'm a Christian, and I thoroughly enjoy studying my own religion as well as others, as do many of my atheist acquaintances. Learning how various religions work, what the evidence for them is, and how they shaped our culture would be very interesting for many people.