When I was in high school, I heard some of the stories about how my classmates cheated. One famous caper started when a senior was able to get into an English teacher's supply closet and steal an important exam. Since that particular teacher administered the same exam to several of her senior classes, it was of particular value as a cheating tool.
The stone-age method of using this test for cheating was pretty simple. A group of students got together and figured out all the answers. Then, they hand-wrote those answers on small pieces of paper and rolled them up so that they could be inserted into the barrel of one of those ballpoint pens that had an advertisement inside. They simply removed the paper that had the ad on it and replaced it with the answer sheet. During the test, it was impossible to see that the test taker was merely reading the answers to the questions from the crib sheet inside his pen. Of course, the cheaters were smart enough to purposely make alternate errors on their answers so that a pattern of cheating wouldn't be detected. It worked. No one was ever caught.