Are there any studies that link phone use inside schools to those issues? Because I can easily believe that declining grades could be attributed towards the use of tablets and laptops being used in classrooms as well which many schools are encouraging or increasing the use of.
As for attention spans I would believe it's for the use of phones/tablets/electronics from a young age rather than the use of them inside of a school itself.
It's mind boggling how poorly designed most of these systems are. These are multi-billion dollar corporations and they can't do a simple thing correctly for the most part when it comes to these systems.
For example, I don't know why this isn't the top and foremost thing but a car should NEVER be able to override when the human driver is trying to do. Sure, beep and adjust if veering out of the lane but as soon as any resistance it met by the wheel it should immediately turn off and let the driver do what they want to do.