Banning phones in school has dramatic results
smh.com.au
smh.com.au
All this "family emergency" crap is, as another commenter suggests, probably mainly about lacking spine when dealing with whiney kids.
There are legit reasons to contact a kid during school hours, and for that you need a dedicated phone (or two) used by assistant principals, with a phone number published to parents. That's how we did it in the 70s, with POTS.
I'd get in trouble just for bringing card games.
What changed?
I think (hope!) this is just the pendulum swinging from "my kids should be my friend, so I won't support things they don't like even if it's against their best interest" back towards "I should parent my kids effectively, even if they they're upset with me for a few years". I feel like a lot of parenting and educational issues these days are attributed to parents who are overly permissive / lack a spine, for lack of a better phrase.
I feel like we had a reasonable compromise when I was at school - you carried your phone on your person and could use it during breaks, but if you were caught using it instead of paying attention in class it would get confiscated for the day (and detention etc. issued as appropriate for repeat offenders).