“Public school principals (In NYC — I’m not familiar with the rest of the country) are supported from below by numerous AP’s, coaches, non classroom professionals (therapist, SBST members, etc.) and multiple office staff.”
One reason is the size of the schools. There is a public high school near me with over 4,000 students. Another has 2,800. By comparison, the largest of the three Orthodox high schools in my neighborhood has under 400.