The best thing you can do is talk to your parents before it arrives. Tell them you and everyone else struggled in this class but you are going to keep working hard to raise your grade. I would hope they will be open enough to listen to you since you are coming to them ahead of time.
You should be very proud of your grades, not all kids care as much. In a tough class you can't always be expected to pull a perfect grade right off the bat, the rest of school and life in general isn't like that! If you did it wouldn't be a challege would it?
Good luck, by the way, we're practically neighbors. Turlock here.