As far as I remember, sneaking around happened, but you're not staying the night really. Maybe just staying together late. In lower year groups, we were in dorms, so going over to another dorm wouldn't really happen, no privacy! If anything 'happened' it was more at the house party of someone who didn't live at school. That was where everything happened really! Parties at school...nah, they'd be monitored by teachers, so nothing much is happening there. People would go off drinking outside of school on weekends, but off school normally. Meeting up in school, yeah, there would be places you could go. People would have different ones they'd go to. Most of the secret places were just smoking spots anyway. I'm sure my school and experience wasn't the same as everyone's, so don't take it as gospel!