What can I do to get a Gemini man to stop cheating and focus on his studies?

By cheating, if you mean him flirting with other people: try to talk to him about it. Gemini tend to be flirtatious by nature. He may not intend it as cheating. Let him know how much it hurts/bothers you. By cheating, if you mean cheating on homework and exams: talk to him about it. Ask him why he is cheating. Maybe he needs help understanding the material. See if you can help him with his studies. Also, tell him that it is not always important what grade he gets in the end, but that he simply does the best he can--he might simply be anxious about getting that A.