My kids' middle school had a similar problem. For example, three kids out of a hundred would cause a problem during lunch, so all hundred kids in the grade had to sit in alphabetical or some pre-determined order for the rest of the year. My kids said everyone including the teachers and kids knew who was causing the problem, but everyone had to pay for it. I think the school was afraid to single out the "trouble makers" (they were just throwing food or yelling or some other typical bs) and contact their parents, so they just made all the kids pay for it.