While much of the debate in K-12 education reform today focuses on students' academic performance and college and workplace readiness, an examination of the mission or vision statements of most school districts reveals another key priority, often overlooked in the debate: cultivating active, involved community members, citizens and future leaders. Public schools have a vital role to play in contributing to the civic development of students, as the skills of citizenship--including leadership and informed decision-making--must be learned. Citizenship education teaches the values, knowledge, skills and sense of commitment that define an active and principled citizen. While the importance of teaching students about American history and institutions, constitutional rights and the obligations of citizenship is undeniable, equally important are opportunities for students to practice complex civic skills such as problem solving, leadership, persuasive writing and building consensus, as well as simpler skills like communicating with public officials about an issue of concern. This issue of "The Progress of Education Reform" examines research on what constitutes citizenship education, how citizenship education contributes to the acquisition of 21st century skills and civic learning opportunity and achievement gaps.