Let’s start with the basics. People everywhere generally agree that the purpose of schools is student learning. Further, people are generally in agreement that the most significant factor determining whether students learn well is teaching quality. Teaching quality is improved through continuous professional learning. Today, the most promising context for continuous professional learning is the professional learning community. The three words explain the concept: Professionals coming together in a group — a community — to learn. How did we arrive at the professional learning community as a structure for school improvement? We’ll examine the concept’s development. TEACHERS AS SOLE PROPRIETORS For much of the history of education, teachers worked in what were architecturally characterized as egg crate schools. Teachers typically worked in classrooms with no