Parents, Students...........---->> My Nightmare

What can I say? It's like a nightmare come true. I keep on questioning myself, " Am i good and capable teacher?" Oh God....I want to cry everytime i remember their words. The problem is the students got bad score for Reading Phonic. I've already done my best to teach them. If they still get bad score, am i the only one to be blamed? The parents didn't know how the condition in the class room, they even didn't know the way i am teaching. They don't recheck that one to me directly but they speak to the principal. The words that they spoke to me were means. They said that i am incapable of teaching, don't know the student's character. I can't continue this again. May be i have to stop being a teacher.