I also teach building to any student that would like to learn. So far since I moved to Vegas I have only had two students want to learn how to build. One was 12 and one was 70. What I no longer do is teach anyone that isn't old enough to drive and has there own car. When I have taught kids I turned into there weekend bus driver and with all there gear and my own I couldn't bring out what I would have liked to due to room in my van. I have found that young people learn to fly in days and older people take weeks, sometimes months to learn. I'm OK with that as long as they take the time to keep learning. I do have a couple of old students that may only fly once every few months and get upset because they don't get any better at it. When they do come to the field they may only get in one flight and BS with the other guys, that's OK too but then I don't want to hear them complain about not improving.
My grandson was 4 when I had him on the box, he is one that doesn't want you to help him, he likes to figure it out by himself, at least he did the turns and things I told him to do, you just better not try to reach over and touch his TX!! He is 6 now and pretty good on the controls but is still only flying three channel. His next trip here I will have him on the box with a 4 channel plane again, I even like to let people buddy box with my Hots. No one else flies it by themselves but I do let people give it a try as long as I can take it away from them if needed. I loan all my new students my SIM too so they can practice what they did on the trainer.