Kids should not have cell phones in school or out of school. My nephew 14 has a cell phone and during the school day he is always posting stuff the facebook.
A teacher facing a high school class today will not see a single student paying attention to the lesson. They will see the tops of the students' heads as they attend solely to their cell phones, texting, shopping, watching movies and catching up on email. I often told my students that I had never seen any job ads asking for people who knew how to use a cell phone, but I'd seen plenty for engineers, accountants, nurses, etc.--none of which they'd be qualified to do ignoring lessons to play with their phones.