Kids and Cell Phones...How old should they be to have one?

At what age do you think children should have a cell phone?  I look around and see kids in elementary school with their own Iphone and it boggles me.  Does this little person have a job?  Smart phones can cost around $500 - $700 easy...just for the phone never mind the plan.  Half of the adults I know walk around with cracked screens never mind a 9 year old who has no concept of money.  Are they so busy in life already that they need constant contact with friends and exposure to the internet at the palm of their wee little hands?

Ok...even if as a parent you think, hmmm...I want to be able to communicate with my child at any moment so they need a cell phone...but do they need that smart phone though?  What about a good ol' normal can get and make calls/texts kinda phone?  Why do they need to be on Facebook, Twitter, Instagram and God knows what else?  That's a whole another post I'll rant on at a later date! ha, ha

I was sitting in my daughter's new student orientation at the middle school yesterday and the cell phone topic came up.  They gave the whole "don't use your phone during class time to text...blah, blah, blah" but then they threw me off when a teacher stated, "you may use your cell phone during class to help with your work at times".  Well, of course my 11 year old turns and looks at me like SEE MOM...EVERYONE HAS A PHONE BUT ME!!!  So now what do I do from here, get her a phone that I don't feel is necessary just because now students are using smart phones during class instead of books to do research.  Yes, Yes...I know get with the times stop acting like I'm elderly and oblivious.  

My daughter does not know this yet but I will get her a smart phone before school starts next week. However, it will not be the latest android or Iphone.  There's not enough chores in the house to cover the cost of one of those phones if she breaks or loses it.  

What's your opinion?  How old is old enough for a cell phone?