This paper illustrates the historical process of the prevalence of upper secondary education in Japan focusing on the public and private relationships. After reviewing high school policy at the central administration, actual high school supply at local government levels is examined and the harmonious relationship between public and private sectors is introduced. Japanese private schools must fulfill the same standards of school facilities, teachers' licenses, and curriculum as those of public schools, under the control of school education laws with a few exceptions. The universal upper secondary education in Japan has been managed with diversities between local prefectures. Japanese education succeeded in the wave of industrialization and constructed a cooperation between public and private high schools. This educational system has supported Japanese development to achieve competent human resources. However, Japan is now facing a new difficulty of determining what further steps to take in the pursuit of top school education in a post-industrialized global world.