Teachers are old fashioned and don't understand. We live by those devices. Heck studies have shown listening to the same song while studying and taking the test improves scores drastically! We might need to call our parents or look something up!
We are moving forward in time, so let the students express themselves however they want. Yes, rules should be set, but why bar them from such a crucial part of growing up nowadays, technology? They can access the internet, and look for more information, only helping their education as a whole.
Go into a public school class and you'll see that cell phones are misused by students they listen and play with it without caring about what the teacher is saying and then surprised when they get work but they can also use it responsibly by using it to look up facts definitions and info.
When you are in class, you need to pay attention to what you are supposed to be learning. Use your earsSince their invention, phones have been a tool for distraction and divided attention. There would be no way to enforce that the phone wouldn't be used to text friends outside class, play on Facebook, or at worst, cheat somehow. Besides, under what circumstances would a phone even be needful? What can a phone provide that a teacher, book, or appropriate Internet resource couldn't?