I always have students go through their tests and correct the ones they got wrong after I've entered them in the grade so they know which ones they got wrong and why. I do this by giving them their answer sheet and letting them correct it and writing down why the correct answer is the correct one or why they may have gotten wrong in the first place.
I don't know if it was because he wanted to do less work or what but a student erases his answers from the answer sheet and uses the answer key to bubble in the right answers and brings it to me telling me that I entered his grade wrong because it says he got a 9 out of 25 when he really got a 20 out of 25. It was infuriating.
Then another girl tried to pull the same thing a little bit later, albeit with a more conservative change. I was very disappointed in them.