This Quiz access rule plugin lets you require users to agree to a statement about not plagiarising before starting a quiz.
If you install this plugin, there is a new option on the quiz settings form, and if the instructor turns that on, then when a user tries to start a quiz attempt, they will see a statement about plagiarism and cheating, and they will have to agree that they will be good before they are allowed to start the quiz attempt.
This quiz access rule was created by Tim Hunt at the Open University.