THIS IS UNFAIR!! AN INJUSTICE!! FOOD FIGHT IN LUNCH!! DETENTION IN THE LIBRARY!! :(?

As a former principal, I would recommend that you request an appointment with the principal to explain your side of the story. You must show restraint, and not be accusing or harsh. Any good principal would be willing to look into the situation by asking other students and staff what they saw. If you truly were not involved, he would be able to determine that.