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.
You could have said all of that without being an asshole about it.
Phones can have its usage restricted in school during classes and activities so students (hopefully) pay attention. Outside these ours when studying in their own, they can use it the way you mentioned in their aid with topics they need help with.