School Vandalism

I'm 13 and I use this app to track my period and I know quite a lot of you hate seeing younger kids on here and all, but I have a serious problem. This week someone vandalized my school bathroom. They brought me into the office because I'd been to the bathroom that day around that time and they asked me which stall I'd been to, if I'd noticed anything strange, if I knew who had done it or if I had done it. They told me they didn't think I had done it because I'm typically a great kid. I have never had less than an A and I love my school and have a great time. Here's the problem with this: there were about 70 girls in the time period that the bathroom was vandalized that had been in there and it is almost impossible to tell. I'm primarily a suspect because I went in alone. About 5 girls have came up to me and prodded me about this. They've even spread rumors that my initials are there and that I've done it. I'm sorry to bother you with this, but I need some advice on how to handle this. Anything is appreciated.