How do I cope with the situation at school?

I am currently in my 2nd year of A Levels at 6th form. This year has been the worse one imaginable. The teaching has been awful and most of the teachers are nasty to you. Last year I achieved an A and a B, but failed one of my subjects because we did not finish the course in time. In year 13 i took up philosophy and ethics AS and A2 in one year. This was fine and then we started to be taught by students while our proper teachers sat at the back of the clroom on their laptops. I started to get frustrated as the students taught us by powerpoint that was word for word out of our textbook. I decided to do what my friend does and teach myself at home. All of a sudden I started gettting phonecalls home and letters and the head of 6th form, who is a rude and obnoxious lady started dragging me out of lessons and shouting at me. Most of the time, it was one of these students who kept getting me into trouble. He would not take the register and then it would appear that I was absent when I was actually present in the lesson. My teachers have accused me of lying when I have actually attended lessons. In one of my other lessons, I am the only one who hands work in and actually bothers to do the work. Yet the teachers give me a hard time when I teach myself or I miss one lesson. My friend is in the other cl for the same subject and she has not been to a lesson for 5 months and she has never been threatened or shouted at, at all. Its nearing the end of the year and exams are about to begin, but my teachers have scared me when they say that I will fail unless I go to their lessons. I am teaching myself because all my lessons are, are powerpoints that are word for word from our textbook. How can I cope with this? My friend has got away with not going to nearly all her lessons for months and as soon as i miss any, i am treated like a criminal. what do i do?