Given that teachers are no longer competing for student attention in class, that is one single and quite important positive which doesn't require an academic study and referencing to demonstrate.
I'm not sure what you were hoping to achieve with the request for evidence, but what you're asking is not yet subject to a longitudinal study. The move has certainly been praised by educators, and that should be enough given it's the first or second year year of implementation in many cases, and what they are advocating for isn't a social taboo, nor draconian.
But phones shouldn't be competing with the teacher during class in the first place!
Are we going to draft laws to ban fiction books from school because kids might be reading books during class? Because I literally saw that happen when I was in school. Obviously unrelated things to the class shouldn't be used during class, but these phone bans go beyond just the classroom.
I ask for evidence, because all the evidence I've seen on it has been effectively nothing. The studies are vague, get weak results or draw conclusions that aren't supported by the study. Eg there were some Spanish regions that banned phones in school. Soon after they scored higher on PISA, this was naturally used to support the ban. But the next round they scored lower than before the ban.
Banning phones in schools seems almost entirely to me about "kids these days are ruined". Phones are just the easy culprit to point to. Meanwhile phone bans do infringe on the liberties of the kids. You are taking something away from them.
I'm not sure what you were hoping to achieve with the request for evidence, but what you're asking is not yet subject to a longitudinal study. The move has certainly been praised by educators, and that should be enough given it's the first or second year year of implementation in many cases, and what they are advocating for isn't a social taboo, nor draconian.