I would agree with you, despite the fact that I personally have mixed feelings about the whole issue. Now, as an international baccalaureate teacher, it would be best if I did present the opposing view, although it would also be best if it was less me presenting it and more the students "discovering" it. Which is one reason why I don't much use text books. Better for learning, and better for me so that I'm not accused of bringing my religion into my teaching. Even though it's not an official rule, I'm really supposed to keep my religion under wraps because as an authority figure I might influence the children in this way, and this is a big no no. If the kids ask me though, I do tell them I'm an Orthodox Christian, but I don't get into details unless they want to learn more (and then I try to present it as a learning moment, rather than as an attempt to get them to convert). And while I haven't been wearing a cross for awhile (babies have a tendency to yank them off my neck), before babies I certainly did, and didn' t try to hide it (or flaunt it either).
At a regular school, however, I'm not so sure this would happen -about presenting the opposing view, that is. Actually, even at an international baccalaureate school, I think there is a good chance the opposing view would not be presented because many teachers are very much for pop. control and against any religious reasoning for the opposing view. At least in Canada.