Is there any action I can take against my school for accusing me of haring another student?

This girl, lets call her Kay, and I used to be best friends, until her boyfriend started calling me names. We stopped being friends, when I asked her why she told me that my "other" friends call her names and I do nothing about it. We just stopped being friends after that. My "other" friends thought it would be funny to stick a note in Kay's purse making fun of her weight, and I was TRYING to be a good person and tell her that those people put a note in her purse, so she wouldn't get home and find it. The teacher is giving me dirty looks like I did something wrong, so I went down to her and told her what happened. She told me that she was disappointed in me. To be honest Im kind of overweight and would NEVER say anything about her weight. I told the teacher who drew the note and who put it in there. When the bell rings for everyone to get dressed the teacher pulls me and two other girls aside (the girls who wrote the note and who put it in her purse). She hands me a note saying Im kicked out of her cl for two days for "mental abuse to another student". I start to say that I never said anything about that and she told me that its her time to talk and she doesn't want to hear it. I walked away and started crying. My mom called the principal after school and he told her that I have been harring this student for the past month! I went into his office the next day to ask him about this and he had a full page that he was reading off of, telling that Kay told him that I was making fun of her weight. I told him that I NEVER did that, and he tells me that he will talk to me later and sends me to cl. So at lunch, he never talked to me, and I told him I need to talk about the cl ejection. I went into his office and he had this look on his face that was like "what do you want?". I told him that I didnt understand why I got this and he told me "Its final. You were involved. If I EVER hear that you are making fun of Kay for her weight than you will be kicked out of school for 10 days!". I was about to cry by now so I walked out. I have NEVER and would NEVER make fun of Kay about her weight. I dont understand why I got this, Its going to bring my grade down to a C. Is there ANYTHING I can do?