My sister use to work in a school and she would shake her head when she saw students who couldn't be more then eight years old with these devices. She felt they were way too young to understand the responsibility of having such a device. I have to agree with her, I don't have a smartphone yet there are kids out there with one.
I take no offense to this if the kid has actually earned the phone themselves not just had it handed to them by their parents. I mean when that happens a kid doesn't understand how expensive the phone or the tablet were, they don't understand the maintenance or the charges involved. For me I just think that unless a kid and that included a teenager can afford the device or at least half of the device then they shouldn't have it. That was a philosophy my parents had they provided us with all the necessities of life, but any of the additional things we wanted we had to earn them ourselves. This taught us the responsibility or earning money and the responsibility of having a high price item.
Ye, I know that some parents think cellphones are a necessity to keep in touch with their kids. But in this case they are basic phones and pay as you go plans, kids don't need to fanciest of gadgets.