Phone confiscation during office hours

Good day,

I am inquiring in behalf of a friend whose employer, a school, decided to confiscate their phones against their will, without any written agreement nor consent. I would like to ask if this practice is allowed by law and what measures should we take to address this issue?

Look first if your friend violated any provision of the school's code of conduct. If none, tell your friend to write the school for the return of her phone. Tell her if not returned, 'appropriate legal actions will be initiated against the school and the person' who actually confiscated her phone.

"confiscate their phones against their will"
Do you mean confiscate them and give them back sometimes later?
(For instance end of day, week or semester depending of how many times they have been told before the confiscation.)
That's COMMON when a policy is broken repeetingly by individual or group, so the employer get tired of needing to repeet it. But concerning schools it's normaly students, not teachers who break the rules. It's EXTRA BAD if a teacher break a rule, because teachers are suppoused to lead by being good example...

HrDude's answer is far better, in my opinion.

Generally speaking, there are rules and regulations that are in force in any workplace. If the administration can cite any violated rules that will justify the confiscation of said phone, then they will have basis for their actions. Rules and regulations shall have no effect if such rules were new and all employees were not informed accordingly of the new rules in effect in the workplace. Employees are informed usually via a Memo sent to everyone so that they will have ample time to clarify the new rules in effect.

Check the rules or code of conducts that are enforced in the workplace, and see if the employer has any basis for the said confiscation. If not, HrDude's recommendation is apropos.