One of the worst memories I have from school is time one of my close friends decided they'd hand in my essay as there's. I let her see mine on the computer to help her out and they copied onto a disk and then printed it out and handed it in two days early.
First I hear of it is when the teacher tells me to stay behind after a class. He automatically assumed that I was the one who copied seeing as though I handed mine in after my friend. I was so shocked that I barely knew what to say, I tried to convince him that it was my work. I think he believed me but couldn't be sure. I offered him the digital copy but of course my plagiarist had a digital copy too. My friend basically swore on her mother's grave that she was in the right. Argh.
Next day, and I've spent a sleepless night trying to work how I'm going to prove its mine. First thing in the morning I get called in the English staffroom to see the teacher and he apologises for not believing me and all that. Turns out the dumb bitch missed a page when she was changing the name in the footer so that page 5 had my name on it.
She became a bit of a social outcast as all of our friends refused to have much to do with her. So naturally she turned goth or emo or gothmo or whatever so time later. Oh, and I even got a written apology from the school which I have nerdily kept to this day.