Smartwatches may be an overlooked answer to the kid phone conundrum. Watches have the communication and location tracking that parents demand without the distraction of phones.
My watch changed my relationship with my phone very positively, so I offered to get my kids watches as a phone alternative. Not that they couldn't have phones at all, but they'd leave them at home when going on, and not carry them in their pockets around the house. They declined because they think watches are lame and nerdy. Only the most unfortunate kids get watches. They still can't carry them around the house, but…
That said, I canceled my cellular plan on my original one and really mostly use it as a GPS device when hiking. It's easier just to use a watch that doesn't need charging day to day.