This! My experience working with underprivileged (what a strange word) kids is that for many of them, their phone is the only thing in their life that they have at least some control over and that they can consider theirs, and taking it away can solicit extremely negative and even violent reaction, so when I read that the kids did not mind, my first question was "What kind of economic background did they come from?".

This should be at the top. I was wondering how the school managed to enforce this.