Positive youth development (PYD) is an approach to child and adolescent education that provides resources in the school and community to enable youth to reach their full potential and to flourish in a democratic society. The approach draws on various disciplines and legacies in its practices and approaches, ranging from school curricula to out-of-school activities that have long traditions, such as scouting and 4-H clubs. We take note of the philosophical tradition stemming from Aristotle that prioritized acquiring various virtues as the path to human happiness and how virtues of justice, temperance, courage, and prudence are the focus for many present-day programs under the umbrella of PYD. We review the dominant theories of PYD as well as school programs that have been developed to encourage PYD, including social-emotional learning, character education, civics education, and service learning. We also examine the effects of out-of-school programs on PYD outcomes. We conclude with the prospects for PYD and the challenges that remain for its future development.