Well, the first lesson you should take away from this is the fact that you should be reading ahead so that the material that shows up during class is not new. When something seems wrong, tell the teacher why you feel something is wrong. When you're new to teaching, you're bound to make multiple mistakes and give poor information from time to time. It's probably in the best interest of all parties involved to have an interaction between the students and teacher to make sure the correct information is being given out. Any teacher worth their wage should want to give the correct information and as long as you speak up in an inquisitive , rather than accusative manner, you should be able to nudge him into being more careful and possibly prep more for the lesson. I don't think any new instructor wants to be bad at their job from the get-go and will probably respond well to questions.