A loud minority of parents agitated for it enough that lots of schools caved. Educators don’t want phones in classrooms.

No, I've certainly seen a lot of education sector academics argue for allowing them. Just do an internet search for it and you'll find "experts" on both sides. I don't know about the teachers at the coalface, I can imagine their word carries about as much weight as any pleb worker in a bloated bureaucracy like education. I have seen stories about teachers being assaulted bullied and attacked by child and parent when trying to enforce these bans though, so I would be surprised if even those are unanimous on the issue.

There are a lot of parents that have this fantasy in their head of a school shooting in which their child calls them to say goodbye. Or, much more delusional, thinks there'd be anything they can do to help them in the event their child is in one, and can contact them.

Much more likely the case, the phone makes a sound, vibration or otherwise, and gives away the child's location to a would be shooter.