Usually they have the policies, but choose not to enforce them. The rule is there so they can expel or severely punish kids at their discretion, but typically don't want to because that represents lost revenue if the kid leaves.
The biggest pressures on school administrators and teachers are parents through direct screaming and anger, not politics. If you want to have a good schooling environment, make sure to put a parent sized amount of support behind teachers that are good, even when they come to you and tell you little jimmy is being a right asshole and needs to be disciplined
