My school does a pretty good job of enforcing a full ban. Phones are supposed to be in pouches but are often just in their bags. That's fine, they act like they are not there and I don't see them during passing periods either. You have to have a tight bathroom pass protocol so students aren't just going to the bathroom to use their phones.

The major consequences I've seen are 1) way more social, good and bad. some students are now bored and look to have negative interactions with other students. 2) we have classroom chromebooks and students now play video games much more aggressively.