This chapter explores the institutional features and empirical findings of private junior high schools in Japan. While private education at the high school and university levels has been widely discussed, research on private junior high schools remains limited in English-language scholarship. Drawing on Estelle James’s framework distinguishing “excess demand” and “differentiated demand,” the chapter argues that private junior high schools in Japan have grown not due to a lack of public provision, but rather due to parental preferences for distinct educational environments. Using multiple large-scale datasets—including TIMSS, PISA, and TALIS—the chapter compares public and private schools across various dimensions: institutional autonomy, student composition, educational environments, teacher quality, and parental attitudes. Findings indicate that, although private schools have more socioeconomically advantaged student populations and greater institutional autonomy, their educational environments, teacher qualifications, and student experiences are largely comparable to those in public schools. Notably, differences in parental investment and expectations are more substantial than differences in student outcomes. These findings suggest that the perceived superiority of private junior high schools may reflect parental aspirations more than measurable school effects. The chapter concludes by discussing policy implications and the importance of evaluating public education based on empirical evidence rather than assumptions.