At my school, a boarding school, we live in dormitories; about five to eight guys in each room. Everyone sleeps in bunk beds, so hearing (or feeling) if someone is jerking off isn't really hard. During the first few nights of this school-year, no one did jerk off, though; at least not that I noticed. Well, all of this changed one of the nights.
A few of the older students, about 18 or 19 years old, came into our dorm. All of us sleeping there were sixteen. The older students wanted to have a sort of initiation, explaining the unofficial rules, etc.
First, they just talked a bit about the school in general, that we were to respect older students, but the talking soon turned to more, eh, fun subjects. They said that they hoped all of us would 'have fun during the nights.' We didn't really understand at first, until one of them said that they'd have to show us how to 'have fun.'
There were four older students there, and all of them sat down on some chairs in the middle of the room, and then, they pulled their dicks out. They told us to do the same, and I believe that everyone did. Now, we didn't really see each other, but you could hear every single bunk bed squeak, and I could feel my own bed shake.
After some time, the older guys started going around in the room, inspecting us while we went at it. One of them started to jerk off one of my classmates. Soon enough, people started to moan and not soon after, all of us were done. The older guys left us, and told us to have fun.
Since then, most of the nights have had open jerk-off sessions, and some mutual stuff, too. Great fun!