When I was seventeen, I participated in a trip with some class mates and a teacher (though it was not technically a 'school trip') to Europe. Since we were all teenagers, and in a place where things like alcohol could be purchased by kids our age, and considering the distinct lack of supervision by our teacher, some really interesting things happened.
While staying in Lucerne, Switzerland, we had very few scheduled activities and lots of down time at our beautiful hotel overlooking the lake and out towards the mountains, we had just gotten in from Venice, where our accommodations had been hot, cramped, noisy and smelly, so the beauty and tranquility of Switzerland was incredible to us.
On our first night there, we slept very well, but after a day of lounging, and wandering the local town, we had our energy back, and got bored. Some of us went out to buy beer and wine coolers, while the rest of us fished out cards, set up a table and borrowed a stereo system from the hotel staff.
When everyone got back from the beer run, we drank and listened to music for a while, but most everyone went to bed early anyway. After things had settled to the 'core group' of people sticking around for the long haul, it was just I and five girls hanging out in my room.
We had been playing regular card games earlier, poker, black jack and such, but the girls decided that they weren't satisfied with those kinds of games, and decided to play for each other's clothing. While I was not included in the conversation, I was sitting near them, and mentioned that I would very much like to be a part of the game, this didn't seem to interest them, and they told me to get out.
I countered that it was my room, and they could have their game here not, but they couldn't kick me out, so they decided to let me stay as 'ref' and commentator. By the end of the night, three of the girls wore nothing but sheets, and everyone was drunk. Strip Poker DOES make a great spectator sport.