So, some students decide to have some "fun" to celebrate the end of school. Punishment fits the crime and that's exactly what it is, a crime. The students should have been expelled and taught a serious life lesson. It is not a time for babying these young people. What would happen in the real world? Well, since they are heading out in to the real world, get some real world punishment.
Learn life's lessons early and make a success of yourself.