> It’s the right idea but it also puts the burden of enforcement on teachers

As opposed to what? Enforcing rules of the classroom is part of the teacher's job.

I don't understand this objection. What's the alternative? Just let the classroom be a free for all because we don't want to burden teachers enforcing rules? Put a separate security officer in the classroom?

Enforcement becomes easier, not harder, when the rules are uniformly applied everywhere and without exception. There's no gray area and less temptation to bring the phone out because they know they'll lose it wherever they use it, even if it's in the hallways.