When I was an elementary school student, I carried a few coins in the event that I had to call someone on a payphone. (Which happened very rarely.)
But today, we have no payphones. Well, almost none.
So what else could you do, with no payphone? Perhaps you could find someone else who had a phone that they could let you borrow. In years past, it wouldn't have been that uncommon to walk into a store or other place of business, or walk into your school office, and politely ask if you could use the phone. They might let you, or they might not, but it was a reasonable request.
I imagine today that it would come across a lot more suspicious. Why don't you have your own phone?
Both infrastructure and ways of thinking have shifted toward assuming that all individual people who might need to make a phone call have their own personal mobile phone.
Children being assumed to have their own phone is probably more of a grey area, but even so, things have changed, and there may be no going back.
And if they need to make a call, they go to the admin building, and explain why, and use the office phone.
Smart phones are constant dopamine dispensers. They create a dependency and cause human brains to go into withdrawal when not present. Once the science is laid bare I believe they will become severely curtailed in K-12 environments.