Does the above check-box option need a slight tweak / extension?
As it stands, it's a bit misleading. If unchecked, a student's own incorrect answers are still flagged after taking the quiz. Therefore, they can easily deduce which of their own answers were correct, even if the correct answers for all questions are not identified.
This means that (for example) if a capable student takes the quiz and scores highly, they will be able to confirm the correct answers for questions which they themselves answered correctly, and share this information.
I'm aware that it's possible to prevent this by un-checking "Let students see their quiz responses", however there might be cases where it would be helpful for students to see their own responses, but not know (yet) which were incorrect.
Could you possibly add a supplementary check-box so that students can see their own answers, but are not told which were incorrect?
That is a good point. I could see where that would be desirable. Although I doubt it will be done anytime soon. Eventually someone will come on here and mention that you could submit it as a feature upgrade request.
I have always thought that I would like students to be able to see their answers, but not know which ones are incorrect - although I would not use it too much. I prefer everything to be blocked on most of my quizzes to reduce the amount of information sharing between students.