This study is a comparative study on the regional needs and features of new school establishment. It aims at developing a tool for evaluating the validity of school establishment, which would help more reasonable decision-making for new school construction and the class extension in the existing schools. In doing so, it employes a mathematical device - the School Establishment Index(SEI), which consists of class condition quotient, fluctuation quotient in the number of students and school location quotient. To explore the needs of new schools and classes in a district, this study estimates the number of students by a year from 2009 to 2020 and surveys the changing faces of student movement, school and class density, housing development in Incheon Metropolitan City, Gwangju Metropolitan City, Chungcheongbuk-do and Jeollanam-do. Finally, it shows the relative requirement of new schools in 4 districts, which the educational offices can use in the course of planning the student accomodations to schools and making decisions for new school construction and the class extension in the existing schools. This study would be expected to help the reasonable expenditure for school facilities and to restrict overbuilding of surplus classes.