Never stand between the student and their parent.The device belongs to the parent they get to manage it. If you see then using it frequently, call a meeting with both student and parent, suggest a time tracking app (most kiddos lean how to cheat these easily), explain the science of multitasking, explain after this meeting that for the remainder of the school year if the phone is in use at an improper time during class you will ask the student only one time and document the interaction each time (I suggest an email home and CC your admin) always with the same language explaining distraction from class will cause low or failing grades, this is a choice the parent and the student are making and put the kiddos current grade in the email. I also let my student know how to use the phone properly and I model those rules. I tell them I will take calls from my son's school and my admins and always let them know why I am using my phone during their class time. I ask the same of them, if they need to text or take a call they must excuse themselves to right outside my door with a nod or a signal that does not disrupt the class. Is it abused? Sometimes. Does it bother me, sometimes, but I have divorced my ego from their parents decision to give them a phone to take to school and use without consequences. Natural consequences are coming for the phone addicted, I try to warm them and model appropriate behaviors around technology instead of fighting and taking class time to police phones. Plus, sometimes they are useful for quick calculations or looking up stuff on the fly... Phones are here to stay, manage them in a way that let's you keep your sanity and also lets your student know you care. Find a kind policy that respects you, the school, learning, the student, and the parent... even if you disagree with the student and parent. I see a ton of new teachers let their ego get in the way of their primary teaching and learning goals.