Well, there was a time when i laughed loud during a 'religion class' (yes, we have those during elementary, middle and high school, this is Poland... =='), when we had to watch a video in which D&D was portrayed as evil and work of the devil, along with heavy metal, and stuff like he-man. The priest who was teaching probably hated me before, but i got a lot of points for explaining to my class why that movie is full of crap, and why people who believe in something like that are idiots.
The effect? Well, we had a class trip that June. And i ended up with GMing a chaotic little game of Kryształy Czasu (not quite the local DnD clone you would expect - the rules are so complicated you need a math grade to even understand them) for half of my class (thirteen people, age 16-17). It was fun. A lot of stupid things came up, but it was fun...