This paper presents data from two studies--a nationwide quantitative research and an ethnographic study--on Greek schoolteachers' attitudes towards immigrant pupils' bilingualism. The quantitative data come from a large-scale questionnaire survey, which aimed at the investigation of the needs and requirements for the implementation of a pilot programme teaching migrant languages in Greek state schools. The findings provide an updated comprehensive view on how Greek teachers perceive their pupils' bilingualism and the inclusion of their heritage languages in the state school. Complementing and enhancing the quantitative data, the analysis of four teachers' semi-structured interviews, which were conducted in the context of the ethnographic study, provides insights into their language ideologies, which underlie their language views and school practices.