One of the major dilemmas when practising critical sociolinguistic ethnography within the field of education is the ethnographer's degree of implication within the studied site (Goldstein, 2003; Martin Rojo, 2003; Unamuno, 2004). How far should the researcher intervene within the daily practices he/she is observing? This exercise of methodological reflexivity implies, amongst other things, bringing to the fore the ways ethnographers negotiate their positions and identities when carrying out the fieldwork, a contingent complex process influenced by multiple factors that demands a continual renegotiation of such identities and positions. The main purpose of this article is to reflect upon the major dilemmas I faced, as a female researcher of Latin American origin, in negotiating power relations within conflictive classrooms in a high school located in the centre of Madrid. The conditions under which relations are negotiated give rise to consequences for the entire research (i.e., data collection and analysis, amongst other things). (Contains 5 footnotes and 4 excerpts.)