To some extent this is one of the recommendations of the PISA 2022 report, but it comes with a big caveat:

> 4. Limit the distractions caused by using digital devices in class >Students who spent up to one hour per day on digital devices for learning activities in school scored 14 points higher on average in mathematics than students who spent no time. Enforced cell phone bans in class may help reduce distractions but can also hinder the ability of students to self-regulate their use of the devices.

I don't think a simple blanket ban on smartphones in schools is likely to solve much.