I'm relatively young myself, but pagers were the limit of technology when I was a student. Cellular phones were in use, but were waaay to cost prohibitive.
Now with phones being so damn cheap, and service not being very expensive either, I have seen kids of middleschool age walking around with cell phones. I got by without one until I was 21, and could function without one. It's convenient, but it's a convenience a child doesn't need.
When I have kids, if they want a phone, fine, they'll get the cheapest piece of shit. Then I'll limit their calling so they can only call me, and their mother, and only receive calls from me and their mother. Or no phone at all. If they want to call their friends, they can get a job and buy their own phone and pay their own bill.
There is no need for a kid to have to call anyone from school. In an emergency, the school has the parent's phone numbers. If the kid needs to call for non emergency stuff, they can use the office phone to call mom or dad. If the parents have an emergency, they can call the school. It ain't that hard.
Cell phones in the classroom = bad.