In college I had a professor suddenly announce mid exam that it was OK for everyone to take 60 seconds to cheat as they wished. The 60 seconds passed with everyone basically looking at each other wondering if he was serious or if this was a trick. I never asked why he did this. I can only guess he saw someone cheating and this was a way to put an end to it.
In H.S. The physics teacher gave the exact same multiple choice tests for years. Everyone had copies of them. It was sheer laziness on his part not to change anything about them. On the other hand we all had to realize that we were in no way prepared for the Regents exam so in the end we still had to study the material.