Anyone could initiate a 'porn break' but there was substantial risk of being called a 'gayer' for those who refused to take part. They do so by giving the command 'porn break,' which must be loud enough for the all members of the class to hear.
As many people as they dared stood up at their desks and re-enacted the movements of their favourite porno flick (by themselves, no homo porno was allowed). This may have envolved getting oral, doing anal, straight, the 'wheelbarrow' or any other sordid image we could conjur up. Props were allowed including chairs, tables, cuboards, bins and board rubbers.
This went on for a maximum of five seconds, when everyone sat down and carried on working in complete silence as if nothing had ever happened.
Half the fun was the expression on the teachers faces, where you could see 'did that just actually happen?'. Most of the hard pressed staff chose to ignore it. Until Russell, a genius playground terrorist, took it too far and ran up to a French teacher during a porn break, and pretended that she was giving him a blowjob, then fucking her, then he bent over in an act I can only guess, that she was rimming his arse. We all paused, mid-pump and gaped in awe and respect. We quietly sat down as Russell was dragged from the room by the scarlet faced teacher.
Porn breaks dwindled away after that, Russell was the undisputed king and in that summer of 1992 he became a hero for a brief time. Until he got suspended for making hoax IRA bomb threats to the staff room....but that's another story.