In this paper we discuss results from a project that investigates the socio-academic trajectories and potential processes of educational exclusion of immigrant adolescents in Spanish compulsory secondary education (ESO, for students between 12-16 years of age). The major part of the study is a multi-level holistic ethnography of an urban secondary school in the south-west of Madrid conducted during two academic years (2007-08 and 2008-09). In this article we focus on four dimensions of the institutional life of the school: (1) Institutional discourses and procedures around Latin-American students; (2) Counseling and support work with immigrant Latin-American students; (3) Some aspects of social life the classroom; (4) The place of different expressive styles in the semiotic landscape of the school. Our analysis suggests that the institution explains immigrant students' educational experiences and responds to them pedagogically through strategies and mechanisms of 'externalization'. Also, different social processes position immigrant students as 'guests/visitors' in the school. This paper is published in Spanish.