No teacher (or parent) has ever managed to lock down a computer that was in my possession to a level where I wouldn't get distracted by it. You could shut the power off, and I'd still be poking around the hardware. I spent hundreds of hours programming my calculator instead of paying attention in class. Informative? Yes. Distracting to myself and those around me? You bet.

I completely agree with your phone take. There is no level of administrative control that can remove the distraction from the device.

Why would you think laptops are different?