If your kid plans on playing almost any High School sport they will need a phone. Team communication is done through messaging apps like GroupMe.
The same goes for most school clubs or student government.
Most schools use Google Docs to handout/turn in assignments... Unless you kid plans on hauling around a Chromebook/laptop at school they need a way to get those assignments IN SCHOOL.
Most part-time jobs require some type of phone to receive work schedules and updates. Some jobs even require some type of phone.
All of our ward youth activities are sent out over group messaging apps.
Any type of social life will require a phone.
If you ever have dreams of your kid playing any sport at the college level they better know how to handle social media. Due to NCAA regulations, the preferred communication between schools and recruits is currently Twitter. If your kid doesn't have any type of Twitter presence good luck getting recruited.
... in short... you can either teach your kids (aka.. take control of your kids) phone habits...
... or go full Amish