Smart phones in pockets being a problem is supported by robust psychology research. People do the worst at tasks when phones are on the desk in front of them, worse when phones are in their pockets, and best when phones are left in another room even if the devices are turned off, in all cases. It’s even worse if phones are on even without any sort of notification, like vibration. (And, obviously, notifications make things increasingly terrible.)

The research is not at all unclear or anecdotal; it is very strong. Phones are damaging to attention, task completion, and learning. This is established; the only disagreement is to the degree of the effect.

Re: phones in “class”, I think we’re misunderstanding each other due to terminology. Here, “a class” means a single instruction period. I thought you were for banning use during instruction time, but against phones being fully banned at school, but if you mean “class” to be the entire time from first bell to last bell, then we’re in agreement. No smart phones at all during school hours would be a good step.

Hopefully, that might also make parents more aware of the damage smart phones are causing and support a societal move away from giving youth addiction machines.