DD1 is Year 11 and has had a couple of 'boyfriends'. The first real one began between Year 9 and 10 in the summer holidays.
AFAIK, it involved hanging out with other couples (her friends and his friends, it seemed), holding hands, cuddling, arms round each other as they walked, and kissing from time to time. The first one petered out when they were back at school in Year 10, but they're still friends now. All bar one of the other 'couples' petered out, and one is going strong to this day.
She then had another boyfriend who lasted maybe 3 months or so, at the end of Year 10 over the summer, but lasting into Year 11. AFAIK that took the same sort of format, although they did hang around just the two of them from time to time. I'm almost certain a fair amount of kissing went down (caught them kissing outside the school gates, in town, in the living room etc) but I'd be pretty sure that it went no further. They split up when he 'cheated' at a party by kissing someone else. He's the year above, so she doesn't see him any more, and I'm pretty sure he's been branded a b*dard by her friendship group, a sentiment I agree with wholeheartedly.
I suspect she has a new boy interest on the scene, as she's spent a lot of time with him, and there's a lot of fuss as to what outfit to where when he's going to be there 
. Again though, most of the interaction goes on in a big group.
DD2 is Year 9, but is very quiet and shy, so I suspect she might be a bit slower on the uptake. It took her a while to make a solid group of friends (mainly girls), and I think she'll enter the boy world very cautiously.
DD3 (Year 7) and DD4 (Primary school, so no worries there yet!) are much more like DD1, so will no doubt throw themselves headlong into the boyfriend scene in due course.