How to offer fair exam retakes? Within my college, teachers generally allow any student who earned a D or lower on an exam, to retake the exam. While I do not need to follow this policy in my courses, many students expect their instructors to offer retakes.

I would like to offer retakes, but see two problems:


Setting a fixed cut off at a "D" seems unfair to students. If a student earns a single percentage point more than this, they cannot retake it, but the student who retakes it stands a chance to earn a full A.
Allowing all students to retake would create too much extra work for me. Some students who earned a 95% would still try to retake it to get 100%.


If there a fair method of allowing exam retakes that discourages every student from taking them?
I think the easiest way to handle this is to allow anyone to take the exam again. However, the caveat is that the retake replaces the previous grade, whether or not it's a better grade. A student who got a very high grade (such as 95%) on the first exam is unlikely to retake an exam to gain five points, when there's every chance the grade could go down by taking the exam a second time.

What one other professor did in a similar situation was to make us choose between keeping the grade on the exam or taking the repeat exam before we saw the grade on the first exam. That is, you could either get your exam back and take that grade, or leave it sight unseen and take the second exam.