I'm agency supply a school I used to regularly supply in has started saving money by putting the cover lessons in the school hall with 2-3 cover supervisors. The hall has several entrances and exits that are in regular usage, doubles up as the dining hall, and is the location of the only toilets in the facility. Work is rarely given, and the environment makes working impossible due to the inevitable noise and chaos that ensues. Sanctions are basically nonexistent due to the number of students. Kids could easily just leave without being noticed.
Is this being done elsewhere? I know they've apparently based it on a 'successful model' from somewhere and SLT are basically burying their heads in the sand because it's saving them a few thousand pounds a day.