Piglet, in the last college I worked at I did that, placed a star in the corner of their paper if I caught them doing something. Then during the exam they caught on that something was wrong and when they handed the papers in they tried to ERASE (by various means) the star, so like that's going to work! Then they had the bloody hide to make excuses about why they WEREN'T cheating etc, despite me watching like a hawk. It's so nice now not having to deal with this in my new place!