I think it's silly there needs to be a formal rule. However, it used to be that if a student was being intentionally disruptive, for any reason, the teachers had the support from parents to forcefully bring that child into line. Now, schools need to codify every last possible infraction to keep from incurring the wrath of over-protective parents itching to sue.
As a parent of schoolagers today gentlemen -- this is unfortunate, but I see why stuff like this happens. Sad really.