In my little corner of MCPS, the majority of middle schoolers bring their phones to school, comply with the rules on not using it during class, and have data plans. Heck, half the 5th grade girls at my child's elementary have phones too (with data plans). Some have the newest iPhones, some have the second newest because it's their parents' cast-off, and some have non-Apple products that look just as snazzy.
We're the outliers. My 8th grader just got a iphone 6, withOUT a data plan and it's to call me if he misses his bus or has to text about something urgent, like his multiple allergies and health issues. Yes, he takes it to school but keeps it in his backpack and the backpack is in the locker. He doesn't take it out on the bus because he gets carsick if he tried to text on the bus