high school problem

I am 18 years old and a senior in high school. I recently got angry at another student outside of school and decided to make a computerized picture of the student, which made it look is if she was holding alcohol and smoking. Although this picture did not look realistic, I posted it on the internet for a period of approx. 30 minutes. Within this time, she saw it and told the school principal.
The next day, I was called down and told that I was going to be kicked out of my extracurricular activities because I broke a contract that I signed at the beginning of the year.
This contract states:
"I agree to not display inappropriate images on the internet, for example images that promote alcohol and or drug use."
I need to know whether or not I can fight this decision and whether or not what I did falls under the contract. The contract seems to be very vague so I am not sure if my school actually has a valid case.

Thank you.

[randalljd]

What contract is that? ...did all students sign that?

Just because a contract is perceived vague doesnt invalidate it. You shouldnt sign a vague contract for your own protection. Based on the information you have given it doesnt seem vague at all. It specifically mentions drugs and alcohol. You shouldnt have posted the images. Don't waste your time, money or energy fighting this. Take your punishment, which you deserve, and next time learn to handle your conflicts in a more mature manner.