Schools have long been recognized as key institutions affecting social cohesion. Schools foster or retard student tolerance, respect for diverse others, and sense of overarching common identity and values. They prepare citizens with the knowledge and skills needed to participate effectively in a democracy. Schools themselves are an object of democratic participation. Thus, schools affect social cohesion both through their affect on students and through their conduct as societal institutions. This article reviews a variety of means by which schools can either promote or erode social cohesion.