Role of Principal by Shelly Habegger. How does a principal know when schools are successful?

Role of Principal by Shelly Habegger. How does a principal know when schools are successful?
Order Description
1. provide one or two real world examples.
Note: I am a middle school math teacher which means I teach 6, 7 and 8 grade math. I am also an ICT teacher.
Provide sufficient background information and how your examples support your argument.
Provide how your point relates to School/District Leadership.