Haha. When I went to France with my college, on the last night we were promised a visit to a night club, but we got taken to a restaurant instead. We ate and then were given free time in montmartre (an area full of bars) for 3 hours.
So everybody went to bars. The problem was that everything in bars cost so much and a small group of us went and bought some vodka from a supermarket and took it back to the hotel, got slightly wasted but not noticeably and thought nothing of it.
Loads of other people stumbled in absolutely WRECKED, including my roommate, which culminated in a search of our room and the vodka being found. I got the same level of warning from my college as the people i stayed up all night trying to keep alive -_-
Anyway, the relevant part is that although the first few weeks back were 'frosty', my French teacher was professional about it, as was I of a fashion, so lessons were fine and I can honestly say she was my best A2 teacher. It won't bother them one bit.