Recently, as school failure or crisis is becoming a worldwide phenomenon, it is argued that public education is losing its efficacy at the turn of the history of civilization from the industrial society to the knowledge-based society. In the relation to this argument, this paper examines the efficacy of the fundamental ideas and social functions of the public education system and their relevance to the present times. The ideas and functions of public education are still valid. The school failure or crisis may be because it can not fulfill its ideas and functions any more; because the specific contents of the ideas and functions are losing the relevance to the times; and because the system adheres to the traditional way of fulfilling the ideas and functions even if it has to change the way of fulfilling them in accordance with the change in the context and environment of the fulfilling. Therefore, rather than denying the efficacy of public education, we should make an effort to realize the ideas and perform the functions fully on the one hand, and to raise their relevance to the present times on the other. Over the past two centuries, the public education system is expected to fulfill the ideas and functions of educational equality, social integration, and development and provision of industrial manpower. Through the adjustment, the ideas and functions of public education should enhance their relevance to the present times. First, the perspective on the equality of education based on ability should be changed from the perspective based on the view of the uniform and vertical type of ability to that based on the view of the plural and horizontal types of abilities. Second, the policy emphasis of educational equalization should be transferred from the equalization of educational opportunity and conditions to the equalization of the educational outcomes. Third, the principle of social integration the public education is trying to meet should be changed from the principle of national integration and the status quo emphasizing uniformity and universality to the principle of social cohesion through the autonomic and effective management of social conflicts and tensions among a variety of social interest groups on the one hand and the principle of social inclusion through the prevention and overcoming of social exclusion on the other. Finally, the focus of manpower development by public education should be shifted from the development of standardized labour suitable to the mass-production system to the development of human resources with creativity, flexibility, and self-directed learning ability necessary in the knowledge-based society.