My oldest goes to a top, selective public school. They barely enforce any phone rules at all and for some classes just tell the kids to use them. Sometimes is just for research, but also you can do things like run a scientific calculator app instead of paying TI hundreds of dollars. And even normal kid stuff like playing video games during open periods is allowed. Doesn't seem to be hurting performance. We have never limited her screen time, she watches loads of stupid youtube and yet she's still going to be at least in the running for a top tier engineering school when she start applying.

Sorry this was just bragging, but from what I've seen this applies equally to all the kids at her school.