Although the effectiveness of a school is mostly evaluated with the students’ achievement in core lessons in national or international exams, “School Effectiveness” is a multifaceted term which includes the qualities of different parties., School Effectiveness refers to the level of goal attainment of a school and it is one of the major factors affecting students’ success. High expectations from students, educational leadership, monitoring progress, parental involvement, staff professional development, positive classroom climate, and high level of school resources are the main factors creating effective schools. In this respect, this study initially aimed at designing a Likert type School Effectiveness Scale to define the qualities of effective schools, and secondly analyzing the result according to the socioeconomic status. The study was conducted in 9 state secondary schools, 5 located in low socioeconomic status neighborhoods and 4 in high socioeconomic status neighborhoods. 388 administrators and teachers participated in the study. The reliability analyses revealed that Cronbach’s Alpha coefficient of the scale is 0.962, and the scale consists of 5 factors. These factors explain the school effectiveness phenomenon up to 69.60%. The discussion of these findings gives better insight about the factors which create effective schools.