I made a conspiracy theory when I wasa in school and had it posted on the net by a teacher for a demonstration. The basic idea was when the school systems in England moved from a 3 tier to 2 tier system, the government had organised this to increase sales of drugs to younger kids (moving them in with the the upper school addicts).
By the next day it had been linked with 3 celebrities and several government officials, and was one of the top theories
