The main thing with teaching anyone to climb is to show them only the right way to do a thing, and be patient. I have found that it's better to give them a minimum of options too. For example...if you're using drt style and are showing said newbie the climbers hitch of your choice, only show them one. Blakes for example. Don't also give them the tautline, the VT, etc. It's too much too soon.
When I was just starting out some of the "old timers" would yell and carry on if it took me 15 minutes to get up a tree that would only take them 3. And heaven forbid using your "chicken strap" while going up. Yea? Well if something goes wrong, a slip or loss of grip etc., they're not the one hitting the dirt.
Give the lad time and all will be fine.