Managers I've dealt with in the States are usually degreed professionals; the more experience they have the better they are. The minority are the good teachers advanced to be assistant principal. One suburban high school of about 1,200 students had two such asst principals, ie, both were advanced from teaching positions in which they were excellent. However, they were anonymous. I barely remember their faces. I never saw them out and about. Maybe that's good but somehow I doubt it.
In Korea asst principal is a prestigious, career-capping position awarded after some caliber of a teaching career. The asst principal has a huge desk and presides (looks important) over the main room of teachers and their individual desks, which is his (literally "his") only activity. The principals are the guys who know someone higher up. Korean teachers rotate yearly in managerial positions--they are interchangable parts who change nothing and do nothing of significance or even of importance except to keep the machinery of "education" operating year in and year out (mostly out).
In Thailand, the Thai managers of proprietary schools are long time and loyal employees from the teaching ranks, which is why there always are timetable clashes & conflicts at the beginning of each year or semester. It also explains why nothing ever improves or develops in curriculum, quality of faculty, methods etc. Farang mangers carry the water for the school owners. Some farang managers do it shamelessly, others try to appear to be in charge but fool no one, as hero points out. At the government schools I see merit and management positions and responsibilities as having some nexus but it seems more haphazard than it should be. At the one university I've taught, Chulalongkorn, managers were secretive, at the center of pervasive and endemic office politics, and stiff and remote. The Chula managers talk a very good game of modernization, lifelong learning etc. However, on my first day at Chula the coordinator in my faculty said specifically to me that "we don't use the word progress." It didn't take me long to know and recognize why they don't.