Not to pick on you, but it's no secret the AP exam has an essay component. Why didn't you practice them on yourself? Why place your fate in the hands of another human being (your teacher)?
Or perhaps you did prepare on your own, because you were familiar with the test from last year. In that case, ask your coasting classmates the same question when they gripe 
Exactly, perhaps If I didn't already know how to write good essays I would have practiced on my own. I am also taking AP English Languahe which is basically a class in learning how to write a good argument and detect and analyze the ways other writers make their arguments. I know how to write essays well but it does seem unfair for other students who have never had any real formal training on writing an essay not have any practice with their teacher. You have to agree that practicing writing essays by yourself doesn't make you good at writing you need a good teacher to tell you what you didn't do and where you made mistakes. Our teacher really should have made us write ONE essay after the entire school year don't you think.