I am a teacher who works with this age range, and I can say unequivocally that I would want children 12-14 escorted at all times, whether they were my own children or not. There is huge variability in children of this age--there is no "normal." Some this age are incredibly mature and independent, while others have very little situational awareness and could never handle themselves in a crowded public place. Some this age look like they are 9; some look like they are 16. IMHO, a child 12-14 should not be wandering an airport unescorted. Imagine a busy place like ORD or DFW....the poor kid could get lost, miss a connection, become distracted by the shops, lose track of time, etc. Even the most intelligent kids out there do not have fully-developed frontal lobes, so their judgment, decisionmaking, and impulse control are impaired. Not their fault. But I think it would be irresponsible of a parent not to recognize this point.
Yes, cell phones make things easier, and might cause parents to think a kid could handle it. But I would say NO!
At minimum, a parent or guardian should fly with the child to the hub, escort the kid to the connecting flight, and wait until that flight is off the ground. Then, the parent can fly back home, assuming that a designated adult was on the ground ready to receive the child upon arrival in the final destination. A child should be able to walk off the plan and out of the secured area on his or her own, assuming it was a typical domestic airport (not too crowded/frenzied).
What I am thinking is that it might be cheaper in some cases just to pay the UM fee than buy a separate ticket for the parent/guardian.
What do others think? I am especially interested in those of you who are parents and have your own kids this age.