Cheating is Haram (prohibited) in school exams or any other than that. Anyone who does this is committing a major sin, because the Prophet (peace be upon him) is authentically reported to have said,
“Anyone who cheats us is not one of us.”
There is no difference whether the subject is Islamic studies or any other subject. (Part No. 12; Page No. 200) May Allah grant us success. May peace and blessings be upon our Prophet Muhammad, his family, and Companions.