I'd like to ask English teachers a question that has been eating away at me for a while. Having decided to try my hand at teaching not so long ago, I faced some problems I hadn't foreseen. I was much surprised to see that one of the pitfalls was students' desire to stick to a single set of rules. Being reluctant to accept the fact that there are other - possible and grammatical - ways to express the same idea, they begin to feel slight panic every time I attempt to open their eyes to the fact the language is actually a flexible thing. "Tell us which is correct!" Well, either is fine... And instead of encouraging them, the phrase seems to have the opposite effect! We do a lot of exercises and sometimes two or more alternatives are possible (and our coursebook gives only one); and every time I have to choose between admitting the fact, which leads to further explanation on my part and grumbling and rumbling on theirs, and ignoring or correcting or labeling answers that don't comply with the coursebook as wrong; the choice is unpleasant. Perhaps there is a happy medium, but I haven't found it yet.

On the one hand, such reluctance is understandable, as their brains risk getting overloaded with huge volumes of information that they have to process during their crash course. On the other hand, such a "this-is-the-right-one" approach might plunge them into even greater confusion when they complete the course and expose themselves to some real, authentic English. For a long time I myself thought that English was all about strict rules, and it took me quite a while to get used to certain freedom in choosing how to say something; it's too long, inefficient and unpleasant a way. I might be mistaken though.

Has anybody ever run into such difficulty? Do (did) you tell your students that there are other grammatically correct ways to say/express/describe something or do you 'share' this knowledge with advanced students or ones with considerable 'grammatical baggage' only? Do (did) your students feel comfortable finding it out?
I'd be very grateful for your comments.

Thank you.