I don't care how good you are at, well, anything. You can be a genius for all I care. Your teacher says your work is "dissatisfactory"? Their word is final.
When it comes to high school, your teacher's word is law. You come home and say "I worked really hard in English," do you honestly think your parents are going to listen? *snort* NO. All that matters is that little slip of paper in your hand from the school
I'm pretty ok with myself. Sure, we don't always get along, but overall I like myself. But if my teachers start saying otherwise, I'd probably turn on myself pretty quickly.
You are only as smart as your teacher thinks you are.
You are only as talented as your teacher thinks you are.
You are nothing if your teacher says so.
High school has taught me that I am only as good as my teacher says I am.