The research is part of the investigation Institutional Contexts and the Construction of Quality Teaching in Basic Education organized by SOCED – Group Research in Sociology Sociology of Education of PUC - Rio that aims at making a comparative study between two public schools in the city of Rio de Janeiro, one of them showed results above the Municipal average of the standard grade on the Prova Brasil of 2005 and 2007, done by 9th-grade students and the other showed results below that average. The analysis of the empirical material (SOCED Survey) made up of questionaires answered by students’ parents, students and teachers from both schools; field records and interviews with members of the school administrations enabled us to observe some organizational and sociopedagogical features of the two schools which could point out pertinent elements for the understanding of the difference in the students’ performances on their official evaluations in both schools. In order to understand the possible causes of that difference, the investigation could draw up each school’s profile, considering the organizational structure of the school regarding the teachers and the school’s administration; draw up the socialdemographic profiles of the educational agents; besides locating the schools in the organizational structure of public schools in the city of Rio de Janeiro. The pedagogical practice of each school, the family-school relationship and the relationship established with the political power were also elements that arose from the analysis, considering the geographical location of the two schools, both located in northern zone of Rio de Janeiro; however, one located in a slum area, Complexo da Maré, and the other located in Bonsucesso, an important commercial borough of the city.