BOGOTA, COLOMBIA—Like many Colombian teens, Juan Ardila, 15, is experiencing typical growing pains, characterized by mood swings, raging hormones, and a fervent allegiance to a squadron of leftist anti-government rebels, his 48-year-old father Rafael reported Monday. "I have told him that no good can come out of running with the Revolutionary Armed Forces of Colombia," the elder Ardila said. "But he'll snap out of it. When I was his age, I was kidnapping state officials and car-bombing nightclubs in the name of Communism myself." Ardila said he expects Juan to grow bored of drug trafficking and extortion when and if he reaches adulthood.