> For the intelligent & motivated, there will be unnecessary boredom during downtime/study hall, potential hatred for learning/school, and other negative effects.

Boredom is a fact of life, and learning to accept it without forcing yourself to depend on a smartphone is an underrated skill.

> Any widespread banning of freedoms or ignorance of new technologies will have outsized negative consequences.

This argument does not really apply completely to children. And it is not ignorance; they're free to use their phones as they please, after class is done.

I agree with many posters here: phones have been designed explicitly to rob you of your attention span. The amount of willpower and self understanding to deal with that healthily is far more than what most children can muster.