Abstract: Based on the spatial information and the numbers of students of primary schools in Nanjing City in the years of 1995, 2005, and 2012, we revealed the evolution of the size distribution, which was related to the number of students. Various methods, including Gini coefficient, Wolfson polarization index, kernel density estimation, Moran's index, and multiple linear regression, were used in this study. The results are given as follows.1) The average scale of schools expanded. 2) The polarization degree of size structure of the school system reduced before 2005 and then increased after 2005, with the polarization in the old city becoming increasingly prominent. 3) From 1995 to 2012, the degree of spatial concentration of students' distribution reduced and the spatial structure of students' distribution transformed from "mononuclear mass" into "multi-core scatter". 4) Driven by urban planning and the mechanism of self-organization in school system, factors, such as the location, the school quality, the original size, and school consolidation, contributed to the evolution of school-size structure and distribution. The impact of school quality has become increasingly prominent.

Key words: school system, self-organization, size distribution, evolution, Nanjing City