students using their task reports to get correct answers

Hello all, 

I am noticing some of my students have figured out how to use their assignment reports to get the right answers to complete their work for a 100 without them having to work. They are purposely getting questions wrong so that can go back and look up the reports in a different window so by the time they try the task again for about the 5th time they can just search for the question and answer it correctly. Is there a way to disable the reports for my students so they cannot do this. 

Thanks