This one tried to put a repeat sign at the end of the first line of a two-line exercise...
ME: Wait--why did you try to repeat that part?
KID: I dunno. I guess I was distracted.
ME: What was distracting you?
KID: The pencil.
ME (looking at my pencil on the stand): The pencil? So if I move this pencil, all your problems will be solved?