This is what methods courses try to get at. Many teachers are superb technicians and get results with many different kinds of children. The problem is that it is difficult to say explicitly just what it is they do. Unfortunately, pedagogical knowledge is still greatly a part of the informal culture of teaching. Many of the causal factors in pedagogy await discovery.
Chance often plays a great part.
It is difficult to generalize from one successful classroom the circumstances that led to the particular success observed. Also, the application of research results is often constrained by political and moral concerns. In the popular media, good teachers are evangelists, magicians, or entertainers. If we take this to mean that the teacher or principal controls who will be taught, the reality in schools is that such control is minimal. Public schools must take whoever applies.