One of the fundamental historical arguments for traditional public schooling is that compulsory common schools are necessary for a stable democratic society. Horace Mann, the father of American public schooling, argued that common schools would force children from diverse backgrounds, religions, and races to interact with one another and receive instruction on proper virtues. Other people, however, believe that allowing parents to choose the schools they think best for their children could improve essential democratic outcomes by forcing schools to compete and to teach more effectively.

Which system is best to strengthen tolerance and civic engagement in our society? Which theories have the most merit? What does the scientific evidence say?