High school teacher here. I gave a multiple choice quiz to a student this year. I go to grade the first question and instead of choosing option A, B, C, or D, he wrote in his own option and circled it:
"E) I don't know."
He went on to do this for roughly two thirds of the questions on the quiz.
I appreciated the honestly... but guessing to have a chance at some points or at the very least just leaving it blank might've been a bit wiser. Oh well.
Obviously I followed up with the kid to see what the deal was. In the end we sorted things out. I wouldn't say they were on another level of stupid, they didn't "do" school in the traditional way. Ended up having a great year together.