I view smart phones as two dimensional.

On one dimension they are a tool (like a Sheika Slate in Zelda).

On the other dimension they are a toy.

The problem for schools is that the tool and the toy are packaged together.

A further problem is that smartphones are consumer electronic devices, so businesses will strive to make them as addictive as possible and are unlikely to support creating some kind of separation between toy and tool.

So I agree that a ban is probably the best solution at this point. A ban with legal backing so schools can focus on education and not combating distraction.