I remember when cell phones first started becoming a thing parents would get for their kids, especially those who took school trips for sports or debate etc. Even though this was pre-smartphone days, our school had a strict policy of no phones outside of lockers during the school day. If you were caught with one in a classroom, it was taken away and sent to the principal's office, where you would have to get it at the end of the day (typically after a stern talking to).

What changed that teachers started letting kids have phones in classrooms? It is utterly mind boggling to me that it was ever allowed in the first place.

Edit: To clarify, I'm in the US and phones in classrooms seem to be a common complaint among teachers. Something seems to have changed, just not sure what.