I personally think that responsible smartphone use should be learned and practiced, rather than outright banning them.
I think this shows that adults are terribly addicted to their devices and think if they can’t stop using them, children won’t either. They certainly can’t teach how to use phones responsibly if they can’t do it themselves. Unfortunately for children the result is an outright ban.
I can’t imagine UNESCO has any authority over my local school board, but ultimately I agree that there should be heavy limits on kids’ ability to use them while at school. Don’t know if I would go so far as to ban them though.