For example; if you had an accident and you need to call your parents but your teacher wont let you leave the classroom then you can just tell him/her that you need the classroom to be silent so that way you can call your parents and let them know that you need a pair of pants or something to change into because you had an accident or you can have a cell phone on you for a reason like saying that you have to go to a doctors appointment and your parents don't want to write you a note so they text the note to you so that you can show it to your teacher and so that he/she will know what's going on at school.