Absolutely smartphones should be banned, at least during lessons, and at best during the whole time in the school, recess, etc.

Giving a child a dumb-phone in an environment where everybody else uses a smartphone doesn't work. If smarphones are not banned then _all_ will end up with a smartphone, and socialisation difficulties, etc...

This is a case where individual freedoms end up in collective damage. Maybe I'm an outlier here but I'd ban all kinds of social media all the time.