Just read this interesting article about a school in Kent that uses a system, imported from the US, of locking phones in a secure bag during the school day so that they can't be used.
Each student is given a bag (like a pouch, a little bigger than a phone) and they have to lock the phone in it each day. The lock is similar to those magnetic tags that shops place on high value items.
The journalist also spoke to some of the students and it was all a very positive experience.
I've included a share token so it should be available to everybody for the next couple of days;
https://www.thetimes.co.uk/article/e00fb040-822d-4e7e-84cb-13f5b424a9ea?shareToken=658cc0b442e0a4fbe3e9b00bd70dea5b