Squeaky wheel gets the grease. Parents who get nasty enough eventually break down the level of caring by the administrators… it weight of cost of pursuing an action. Not dissimilar to working the refs.
I see, I remember that being a similar situation in my school. But in my experience it was good enough for 90% of the kids to stop using their phones. Cause most ppl’s parents were too busy working or sided with the school at the time