This sounds great, but the reality is that 99% of kids are using their phones to play Fortnite, look at social media sites, or chat with their friends.
These are all distractions for education and it's going to be nearly impossible to police in the classroom without banning phones outright.
I think it would also be better for many adults to do without their phones/electronics for a set period of time.
I think this is the problem. The distractions are so rampant, they would have to have recess detentions for a large percentage of class.
The more logical solution is just to make it a tablet/cell-phone free zone.
Cellphones/the Internet may give us access to more information, but it certainly isn't making anyone smarter. I, like you, went to school in a time where we didn't have cell phones or the Internet and I think I'm better off for it.
We need people that can actually figure out math problems, not just Google the answers. Society will suffer because of it.