Interestingly, the same topic was covered in the book Freakanomics: A Rogue Economist Explore the Hidden Side of Everything. One of the authors, Steven Levitt, developed some of the tools to find cheating teachers. One of the examples I from the book was to look for strings of correct answers that were statistically significant (where the teacher would have erased quite a few of a students answers, right or wrong, and put in all right answers).