This article focuses on the 'native speaker effects' (Doerr, N. M., ed. 2009. "The Native Speaker Concept: Ethnographic Investigations of Native Speaker Effects." Berlin: Mouton de Gruyter) pertaining to the construction of eliteness in Spanish-English CLIL-type bilingual programmes in the autonomous community of Castilla-La Mancha (Spain). We focus our attention on St. Teo's school, one of the target schools of the sociolinguistic ethnography carried out in state-run and state-run private schools in La Mancha City (LMC) -- 2015/2018. Data includes long-term participant observation, audiotaping of classroom interactions in the CLIL subjects, semi-structured interviews with different stakeholders, and institutional documents of the language-in-education policies implemented in the region of Castilla-La Mancha. We discuss how St. Teo's has adapted competitively to local bilingual education policies by relying on native speakers of English as guarantors of educational elitism, distinctiveness and linguistic prestige in the highly commodified market of English. The analysis brings to the fore how the inclusion of English native teachers in St. Teo's bilingual programme has had an immediate effect on the current English-medium teaching practices, resulting in asymmetrical partnerships between content and native English teachers and causing tensions and dilemmas among teachers participating in the bilingual programme.