I am not sure that the analogy with teachers in schools is entirely apt when discussing instruction in skills. Most instructors of skills, particularly of the skills used in risk sports, have to master the sport before teaching it: consider horse riding, sailing and mountaineering as examples. Scuba enthusiasts can advise whether diving is another example.
Having said this, it is difficult to see how a significant body of experienced instructors dedicated to instruction as an end in itself could ever develop, so long as instructors are used as cheap labour. Whenever I have retained the services of an instructor in, say, riding or climbing, I have expected to pay and have paid heavily for the privilege, and have always been amazed at how little flying instructors are able to charge for their skills.
By the way, for discussion which may be of interest to pilots real, fake, old, bold etc, see David Southwood's lecture notes on page 2 of Flying Lawyer's "Old Aeroplanes in C21" thread in the Aviation History forum.