We were never allowed our "dumbphones" in class either though, which made us try to 'sneakily' text. I think students will try this with their smartphones as well.
- Kids play games during the break and that really affects their ability to concentrate during the lesson - they think about how to "move to the next level" or "kill the enemy", not on the lesson subject - Kids don't interact normally, they sit separately looking at their phones - funnily some teachers actually loved that aspect - kids were silent, not running, no shouting during the breaks. I believe that direct human-to-human contact is valuable and can't be replaced with chatting on some app or sharing pictures. - School has no control over the content kids view on their smartphones, so if one kid views porn and shows it to others, the school can be on fire as exposing kids to porn is a crime (at least in some countries) and school stuff is responsible for what is happening at school. - Various "minor" nasty behaviors, for instance kids whose parents can't afford smartphone have to pay those who has smartphones to play games (one can say that it is nothing bad, but I don't like that).
Give it some four years or so.
Well, maybe today things are different when kids are all drugged up with Adderal and Ritalin, and any minor disturbance causes a SWAT team to show up.