That's a broad brush, but as a "person on the periphery" and child of two teachers, I can understand painting with it. When I was attending the diploma mill many years ago, I came to the same conclusion.
If you think teachers-to-be are a bad lot academically, administrators are generally no better but have gone to finishing school... the "commisioned officers" of the government schools, so to speak. My dad had a low opinion of the abilities of many teachers in his district, but his real disdain was for administrators who he generalized as "people who couldn't teach well enough to stay employed, so they got their masters degree and became administrators."
(Dad did respect and appreciate the few exceptions.)