The Peter Principle (over 40 years old) Still a great read!
I wonder if this principle holds true in public education?
Were most administrators highly competent teachers once?
Do most highly competent teachers become adnimistrators?
The following is from the WHAKATE website:
 http://www.whakate.com/lead-articles/the-peter-principle-reaching-our-own-level-of-incompetence/

 In Peter’s Principle, our level of incompetence demonstrates the place where we cease to be promoted, because we are no longer doing our jobs well enough to merit promotion. But since we will not be demoted from a post unless we are ragingly incompetent, according to the Principle, the average worker is not working the job for which they are most qualified; but the job they can perform just well enough to not get fired.

Case in point: Take the career of a school principal. He would start out as a student, and if he demonstrated competence, move on to become a teacher. If he was only an average teacher, he would most likely never receive any significant promotions, but a highly competent teacher may eventually become the school principal. Being a good principal and a good teacher are relatively unrelated though and so there is high chance that the extraordinary teacher (the role he was most competent in) would now only be a mediocre principal. If, however, he proved to be an outstanding one, he would advance in Peter’s Principle to assistant superintendent or superintendent—until he reached the job where he was no longer outstanding enough to reach promotion.

The stage he bogs down in due to mediocrity would then be his defining “level of incompetence.”