So there was this girl in high school who would constantly make jokes at my expense, bully me, and make me look stupid in my AP world history class. It was Friday, the last week before finals week, and the last class of the day. We all left our backpacks in our classroom before going to the gym to do the AP test. I got done early and got back to the class and saw her backpack close to mine. I was seated in the very back of class where no one would see me easily, as there were only a few kids there. We hadn’t turned in our final projects yet and most of the other classes hadn’t had their final tests or projects due either. What I did was take everything out of her backpack while no one was looking (it was a pretty full backpack as she had all advanced classes) and put it into mine and put a few of her other belongings in the other kids backpacks so they would be suspected first. The class was over before she was finished with the test so I went home and threw all of her stuff in the trash. I never said a word about it to anyone and no one suspected me of doing it. I never found out how bad it affected her but I can assume it hurt her grades pretty badly. 

AITA?