Ontario has now passed two different bills banning cell phones in school. It's a great distraction from actual problems. I fully expect we'll pass a third in a few years if our provincial government is re-elected
Teachers don't need a sheet of paper at a legislature somewhere to take away cellphones. They can do that already, and if the kids disobey a legislature won't help. I assume no one is expecting kids to go to prison for having a cellphone
The key thing is that teachers can ban phones in their individual classrooms if the school permits it.
There are many schools in which the senior admin don't institute phone bans (you'd be surprised how common this is).
Legislating it helps maintain consistency and parity between schools nation wide, which is important as it's a quality of education issue, so the policy should be consistent across all schools.
I'm not from North America, but the situation is similar across most western democracies.