Teachers hold the greatest potential impact on student achievement compared to every other in-school factor. Yet schools with the greatest needs, those with a high percentage of low-income students and students of color, face the greatest teacher and leader turnover. They also often have less experienced and less effective teachers, according to national analyses. The Southern Regional Education Board's (SREB's) educator effectiveness team set out to find high-needs schools where teachers and students were beating these odds. What we found was a consistent theme: teachers who learn together teach better. Teachers and administrators at three Delaware schools showed evidence that staff who can create an effective teaching community help students make extraordinary gains in learning.