This research examines whether the educational differences between schools exist or not, and what are the backgrounds and process of the educational differences. The related antecedant researches explain that the educational differences exist between schools and their locations, and view its causal background as mainly socio-ecomomic backgrounds of the students. However, in this research, besides the occurrence of the educational difference by the out-of-school factors, they are derived by in-school factors. Moreover, they are viewed as occurred by the influence of the social dominance structure through the whole process of school education, including the influence by input factors. This research was intended to solve the following problems. ⑴ Are there differences in the characteristics of the school personnel according to the school backgrounds? ⑵ Are there differences in teachers' compositions according to the backgrounds of principals? ⑶ Are there differences in the aspects of the process and practices of school education according to school backgrounds? ⑷ Are there differences in the processes and practices of school education according to the characteristics of school personnel? The questionnaires developed by the researcher under the professional and practical advice from the principals, teachers, and professors were conducted by mailing. The items included in the questionnaires can be classified such as a) school demographic background, b) backgrounds of principals, c) characteristics of teacher groups, d) principals' leadership and guidelines for schooling, e) professional activities of teachers for their quality improvement, and f) the relations of school and community. The subjects were 800 principals of pirmary and secondary schools, selected by the multi-staged stratified clustered sampling. The data obtained from 625 principals was analyzed by using the subprogram of SPSS : FREQRENCY ANALYSIS, CROSSTABRLATION, BREAKDOWN. ⑴ There were differences in the school demographic compositions according to school background variables. The schools in big cities, schools with short history, had higher career principals than those with lower ones. The principals who were supposed to retire sooner were mostly working in large-scale schools. The average teaching career years were more in seoul located schools, prinary schools, large-scale schools, and schools with long history than in those which were not such. The ratio of teachers having teaching careers below ten years was higher in schools of farm and fishery areas, middle schools, vocational high schools and small-scale schools than in those which were not such. The ratio of teachers possessing the M. A. degree was lower in schools of farm and fishery areas, primary and middle schools, and small-scale schools than in those which were not such. ⑵ There were differences in the leadership and guidelines of principals for school education according to school backgrounds. The interview activities with teachers by principals were more in Seoul and metropolitan cities and large-scale schools than elsewhere. Classroom touring frequency of principals was higher in schools of Seoul, middle and small cities, high schools and middle-scale schools than elsewhere. ⑶ There were the existence and frequency of the professional activities of teachers for their quality improvement according to school backgrounds. Teachers' meeting by their subjects existed in city-located schools, primary schools, schools with short history and small schools than elswhere, Lectures by resource persons of community were more in city-located schools, large-scaled schools and primary schools than elsewhere. ⑷ There were differences in the relationships between schools and community according to school background. The perceptions of prinicipals toward the relationships between schools and community were mostly negative. However, their perceptions toward the relations in the aspects of schools and teachers were mostly positive. ⑸ There were more or less differences in teacher compositions according to the backgrounds of principals. That is, the schools of the principals whose career belonged to lower grade had the tendancy to be higher in the ratio of teachers having teaching career below ten years than elsewhere. The schools of the principals who were supposed to retire soon had higher ratio of the teachers having teaching career over 20 years. ⑹ There were difference in leaderships and guideline of principals toward school educaton, professional activities of teachers, and the relationships between school and community according to the backgrounds of principals. The principals who were belonging to upper rank in teaching career had more interview hours with teachers, invited more resource persons out of schools. The principals with administering career had more conference with parents.