Teachers have the greatest school-based effect on the achievement of any child in their classrooms, but highly effective principals can positively affect the achievement of every student in their schools. The difference between a highly effective principal and an average one is equal to two-to-seven months of extra learning per year for each child…

Teacher leaders are teachers who aspire to stretch beyond their classrooms to engage in leadership roles that take many shapes and forms, both "informal" and "formal". These teachers view the school as a whole, see the "big picture" and focus on how they can help improve aspects of the school to result in increases in…