[throwaway50603]

And that definition is not up to either schools or teachers, but parents and potentially the students (depending on the parents).

[germinalphrase]

Clearly, that is not True.

[throwaway50603]

I'm not sure what you mean, it's clearly true where I live.

[germinalphrase]

Good point. I am in the United States. Here, student’s rights are significantly curtailed when they enter a public schools building, and - generally - districts have the legal authority to restrict behavior that "materially and substantially interferes" with education. If school districts in the US want to go “zero smartphone”, their problems would be cultural/political - not legal.