We examine how counselors, teachers, and other professionals at a secondary school in Madrid (Spain) understand cultural diversity and work with immigrant students' educational circumstances. Our analysis suggests that cultural diversity is largely construed as a problem and the explanation of educational difficulties is organized around an "externalizing logic" in which responsibility for educational outcomes is transferred to process and programs outside "ordinary" teachers' realm of action. We analyze these discourses and institutional practices from an ecological perspective: within the context of the local changing demographics of the school, regional/national policy measures around diversity, and wider conceptualizations of cultural diversity in Spain's education system.