I think, given the big slip in grades you should definitely meet with the teacher and figure out what the problem is, but I'm thinking maybe this teacher has a teaching style that is different from what your son is used to. In that, in past classes the teachers were handing out study guides, or giving handouts stating what material would be on the test, and what to review. It seems like this teacher is more verbal and she may say to the class, "We are having a test on chapter 3-6 on Friday," and she expects the students to write it down and figure out what they need to review. It doesn't sound like she relies to heavily on study guides, rubrics, or handouts. Possibly the class is loud, or more disorganized than others and your son is missing some of the things that are being shared, or maybe he is having trouble keeping up. It would be helpful if you could find out if other students are having this issue, too. I know that my daughter is a sophomore, and she doesn't get handouts or study guides. They are, essentially, told when the test will be and what it will cover. They are expected to write it down and prepare accordingly. She is not in honors/AP classes.