when i was a teacher, we had very minimal janitor staff, so i had the kids clean the room every day at the end of the day.
just like they clean their room at home, just like they wash their dishes after they eat, just like they mow the grass of the yard they play in every day.
they were the ones messing up the classroom - and they're LESS likely to mess it up (or more likely to clean as they go) when they know they'll be hitting that mess at 2:50 each day anyway.