Worst thing I did was skip one of my classes in high school. Truancy!
Can't remember what class it was, history I think. Back then I had horrible anxiety (still do, but now I take medicine) and I had to stand up in front of the class and read a report. Normal school stuff, of course, but earlier that week I had already broken down and cried while doing an oral report in French class. I wasn't up for repeating the experience.
So when the bell rang and everyone went to their lockers, I just snuck into the bathroom and sat in one of the stalls for the hour. Came out when the bell rang again and went to my last class. Failed the report since I didn't do the oral portion, but I didn't care, surprisingly.
Whoa, sorry, didn't mean to make it that long. o_o So yeah, worst thing I did was skip class once.