text: If a students have phones, they may forget to turn it off while going into the next class, and if it goes off it will cause a huge disruption. They could tell you that the phone is turned off but that doesn't mean they are telling the truth. they could have it on and when the teacher has her back turned, it can quickly be taken out to ,message someone or read one they just got, which is when they will stop paying attention to what's going on and read about a new piece of gossip, or just get into a conversation with someone. Also if they are taking a quiz or some important exam, they might stop paying attention and waste time on there phone and end up failing whatever it is they are taking. Also if their phone is turned off, they can sit in class the whole time wondering what that last message said, or what did that person want.