I don't think it is a proper boyfriend zoo iykwim. I think everyone in the class has chosen someone else in the class to "pair" off with. I do feel a bit sicky and anxious about it all though, even though I am assured it is normal. I know I did the same at her age, with friends who I am still close friends with now, who are all , but one them , gay--. 
I think it is all about feeling acceptable rather than a particular interest in anything else.
The kiss on the cheek does worry me though. It was a dare and I have pointed out the danger of doing things as a dare and how meaningless something done as a dare is anyway. I felt a bit mean but I have seen dares escalate at secondary school to dangerous levels.
Dh says he had a girlfriend at this age too and said it consisted of walking around his hometown together and the odd game of tennis. Dh grew up in a REALLY rough area (murder a weekend sort of place) and that was all that came of it until I corrupted him
Anxious, anxious, worry, worry....
zoo that sounds like a horrendous night. Can you put on a dvd and sneak off for an hour or two's kip now? Otherwise, like you say, get out of the house for as long as you can bear it or it will be world war 3 
Sending you loads of ((((hugs)))) and lots of moral support and offering a shoulder to rant and cry on.