Given the rote nature of much of our educational philosophy, I'd say that in our current state, teaching a secular class of world religions is a great idea, but that would be most effective under a philosophy that wasn't so dependent on short-term memorization as it's primary method.
What we would get is a meaningless set of terminology that come from various religious doctrine, a cursory reading of each religion's historical spread, and MAYBE some classroom discussion on applications outside of class and/or cultural implications. Unfortunately, we can safely assume that rote learning is necessary only for elementary educational standards. By secondary education comes around, I'd prefer to see less emphasis on rote learning (which kids can google anyway on the 'net), and more emphasis on group-projects, argumentative writing and rhetoric, and further training in logic and the arts.
Were religious education taught within these frameworks, I think it would be successful in its goal of creating generations of people how to work with others in a multi-cultural world. At this point, it would be taught with the goal of creating Self-Appointed Information Dictators trained to work together in an assembly line. Which doesn't really make sense, and it's not really useful.