This one is school-related but it was the teacher who committed potential PD. Even though it's been many, many years, I will remain rather fuzzy on the details on purpose.
The whole focus of French high school is the baccalauréat, or "bac", a test that we must pass to enter university or any kind of undergraduate school, as well as qualifying for the lowest-ranked government jobs. For three years, we live, think, breathe bac. It does not just involve having knowledge but also writing structured essays on a variety of topics. Every year, the bac questions are chosen regionally by a panel of teachers. It's an honor to be one of them. Because of cheating and fraud concerns, the questions are shrouded in secrecy until the day of the test.
One of my teachers (Mr. Teacher) casually mentioned, during my final year of HS, that he was in that panel. Somehow I filed that information away and didn't think of it. During the year, we had a bac practice. We had to take, either questions from previous bac sessions, or questions made up by the teachers, in every topic, and we passed the test under the same conditions as the official one, but of course the results did not count.
Near the very end of the school year, as we were only days away from the grueling series of bac tests, student attendance started going down because some were at home, madly scrambling to catch up. My friend "Rachel" and I, being the two biggest goody-two-shoes of the school, attended until the very last day. On that last day, we were the only two students in our class. We showed up for our class with Mr Teacher, who paused for a minute and then figured out we could always work on reviewing what Rachel and I had produced for the bac practice. The topic was, let's say, fluffy bunnies. He pulled out our essays on the topic, which consisted in analyzing various documents of fluffy bunnies, and we discussed what we did right and wrong.
Two or three days later, it was time for our bac test in that subject. One of the questions was "Analyze those documents about fluffy bunnies." It was all fresh in our memories. I think the documents were either the same, or very similar. We both got a pretty decent grade.
I'm sure Mr. Teacher was not supposed to use for the bac practice the exact question he knew was coming up for the real stuff. I think maybe, when he saw that Rachel and I bothered coming to school until the very last day, he decided to reward us by giving us a pretty big hand. We never mentioned it to anyone, and I don't know if he ever got in trouble for it. It would not have just been professional trouble, but legal as well. Bac fraud is severely punished.