Our kids have smart phones at age 13, but the apps are limited. They can do social media at 14, but only using mom or
dad's phone (ie they don't have Instagram on their device). No internet browser on the phone. Parental controls passcode required to add an app.
No Snapchat while in high school. Obviously when they leave home they do what they want.
It's getting increasingly difficult to navigate the world without a smart phone, including school. Even seminary is easier with a smart phone now.