For me, I do not let them take quizzes over again. Like you mentioned, it would be unfair to the students that where prepared the first time. So, I don't think tests should be given again....unless.....there has been a break down of the learning process. An example would be that the highest grade was a 70. Then you would need to re-lecture using difference learn modes or teaching statigies to better communicate the topic. Then re-test them.
Projects I do different. Since doing projects are where some of the real learning proceses occur, I let them re-do projects. Like all… >>>