Here in the US before phones were everywhere most schools had rules against electronics and how they handled it was to have parents sign a form at the beginning of the year understanding that the use of said items on school grounds would result in the item being taken from the student and returned only to the parent, our school had a three strikes policy on the third strike they would hold the item until the end of school year.

Today I guess parents would bitch about this though because little Jimmy doesn't need to follow rules.

Edit: Changed " they blew up" to "phones were everywhere."