The Branford (Conn.) High School solved the problem of students' using cell phones during the day by locking them up.
Read this article.
The article does not say what other steps, if any, were tried before implementing that policy.
Personally, I don't like it.
I prefer a policy that restricts usage of a cell phone on school property or in a school building or whatever is decided. And then expect the students to follow the policy. (I know. I know... That's like expecting drivers to obey speed limits; right?)
If they don't? Discipline them. But encourage compliance.
Many thanks to the reader (you know who you are) who sent me the article.