I've been in church teaching positions before. When I have been faced with the decision between telling the kids what I think and what the church thinks, I have always gone the middle ground. I present both sides; first the other views and then I finish with "our church believes that _____".

I'm not saying that's absolutely the right course of action. But that is what I have typically done in the past and I've never wound up with any angry parents as a result.