On Friday, the new girl who I've previously written about came in and said that since I gave her a 55, she's going to continue to fail my class on purpose. I said "whatever you want, that's your choice." She just laughed and said "nah, I got you. I'm just kidding!" Then she took the first desk at the front of the room and did all of her work. She was actually the model student.
I think I'm the only teacher she tried to push to the limits, but I guess since I stood up to her I somehow earned her respect.
Now there are only 3 discipline problems left in that class, most of whom I can deal with on a day to day basis.