[vorpalhex]

So that isn't what the document says. Out of 5 cases, only two were constitutional. Both of those were allowed to confirm that a disallowed activity had happened during school.

Specifically in Mendoza vs Klein ISD (from the paper) we see that the continued search of the phone after confirmation of texting in class was ruled unconstitutional.

[mlyle]

Yes, this pretty clearly establishes there's bounds: the search has to be tailored in scope to address a reasonable suspicion of a violation of school policy.

Can a school have a policy about cyberbullying outside of school, and pursue a search in that case? This is untested.

As I said:

"The exact limits of a public school's authority to search mobile devices, to handle events that have partially occurred outside school, has not been established."