OSLO: Having sex with 17 people in as many days, downing a case of beer in 24 hours and making out with a student of the same sex are just a few of the escapades many Norwegian high school students get up to each May in a well-established pre-graduation tradition. Every year, some 30,000 teens about to graduate from high school take part in massive celebrations that go on unabated from May 1 until they culminate in a huge blow-out on Norway's national holiday on May 17. "These festivities have the same feel of liberation as a carnival in a...