lee harvey oswald in the school building with a cheap rifle.
i was in high school. none of the teachers broke down and we weren't released early. have been hearing ever more complicated theories about who, why etc.
vincent bugliosi wrote a good book detailing all the various conspiracies. wasn't sensational so didn't sell many copies. it was a real doorstop.
most conspiracy stories presume a level of competency and ability to keep secrets that is remarkable.