In an ongoing markets in everything piece, Marginal Revolution highlights what happened when one high school banned candy: Students at a high school in Austin, Texas gave their teachers a lesson in the economics of prohibition. When Austin High School administrators removed candy from campus vending machines last year, the move was hailed as a step toward fighting obesity. What happened next shows how hard it can be for schools to control what students eat on campus. The candy removal plan, according to students at Austin High, was thwarted by classmates who created an underground candy market, turning the hallways of the high school into Willy-Wonka-meets-Casablanca…. “It’s all about supply and demand,” said Austin junior Scott Roudebush. “We’ve got some entrepreneurs around here.”