It seems that everything is global
The Chancellor's determination that a mere ban on cell phone use would not be sufficiently effective was not irrational. It is now routine before theater, movie and other cultural presentations attended by adults, for patrons to be asked to turn off their cell phones. Even then there is no guarantee that the cell phone of an inattentive person will not ring at an inopportune time. While the vast majority of public school children are respectful and well-behaved, it was not unreasonable for the Chancellor to recognize that if adults cannot be fully trusted to practice proper cell phone etiquette, then neither can children.