Dumb teacher.. Stupid Punishment..?

Okay so I have this teacher who always bitches.. Recently she igned some homework that could only be done in school, it was about 15 pages long and we could on do it in cl and had about 1 hour to do it. Honestly right there it wasn't fair to the students, so a lot of us decided to collaborate on it and copy sections that we each did. I got caught cheating and I was igned a punishment, in which part was to write a letter to my parents of the events that partook on that day. I wrote the letter then agreed with my mom that my father wouldn't be told of it. (He has anger management issues and I don't want corporal punishment.) I had my mother sign the letter than took it to the teacher. She told me she wants both parents to sign it. I politely told her of me and my mother's plans, yet she still told me she wants both signatures. Is it really her choice to decide on this family matter? As I write this I seriously want her to be dead. And no don't tell me that I should just take my punishment, because that's not what I asked. Nor do I want you to tell me about hatred and wanting her to die, because if I had the decision over her life, I'd end it.