My dad got an email from a teacher, and when he get's home, I'm DONE FOR. advice on not being grounded?

oh jesus. Okay, so recently i've hit a bad patch with my biology teacher. and the geometery teacher is my biology teacher's best friend. For a couple weeks now, my geometry teacher has been literally, PICKING on me. As well as my biology teacher, She has been doing it for 2 years now. My dad knows about it, and we're trying to get me out of bio, but that won't help my Geometry teacher. I have a B in Geometry, but today, she emailed my dad and basically told him that i was the worst most smart alec kid she had ever had in cl, and that i read all the time. Neither one is true. My dad, being as he is about believing everything teachers say, just called and told me that we were to have a long talk about how retarded i am, and that he was "f***ing p***ed* about the whole situation" so. HELP ME. tell me how i'm supposed to calm my dad down and avoid getting grounded in the process. Before 5:30 pm today because that's when he gets home!