Not without breaking several laws, and potentially putting people in danger - how do you call 911 in an emergency if the school is in a signal blackout?
Landlines, voip, panic buttons. People made calls to 911 before the iPhone was invented.
When I was in school every single classroom was wired for landlines and Ethernet. You can also set up your wifi networks in ways that limit certain things and not others.
> When I was in school every single classroom was wired for landlines and Ethernet.
Alright, but they're not wired now. Neither are bathrooms, cafeterias, hallways, or other place where someone might have a stroke, a heart attack, a seizure. And unfortunately, gunmen in school are a thing, and if you're a teacher, scrambling for the wall-phone while you can hear gunshots in the next room over is significantly more difficult than reaching into your pocket for your phone.
I have long thought that there should be a network protocol that would achieve that in practice, but which would let emergency calls through.
Transponders that could be deployed in settings such as schools, hospitals and movie theatres to tell devices to enter a limited mode. Support for the protocol would be compulsory.
But I would think that the telecom industry does not want that.