This study is aimed at exploring whether the policy of assigning students to high schools by their place of residence is problematic in terms of educational inequality in the large urban system of considerable segregation of students among neighborhoods and among schools by class. In this case, the policy of assigning students to high schools by their place of residence is identified as the “Equalization Policy.” Specifically, this study raises the two questions: (1) Is that restricted choice policy disadvantageous especially to the low-income students? (2) If the low-income students trapped in “inferior” school districts are allowed to study in the schools of the affluent 8th School District, is there a possibility that their scholastic achievements will be higher and the ratio of their entrance to the top universities will increase? This study is focused on the High School Districts in Seoul, among which there is stratification by students' achievements and family income. In this study “school district effect,” which was previously used as the meaning of the aggregates of the school effects is redefined as complex effects of interaction among the SES, private education etc. In this perspective, this study has shown why the low-income students could not succeed, even if they should be enrolled the schools in the 8th School District. In conclusion, the low-income students are not disadvantageous especially owing to the neighborhood school policy. This does not support the claim that the policy causes the educational inequality for low-income students. Given that the complex district effect, the low-income students will not succeed in the 8th school district. The policies that could alleviate the problems of complex district effect advantageous to the higher and middle class are required.