Secondary schools in Australia have long benefited from state policies aiming to increase the academic success of English language learners (ELLs). Complementary pre-service and in-service teacher education programmes have been implemented to raise the expertise of subject teachers who teach ELL students. However, subject teachers may not be receptive to learning from such programmes. This article explores the attitudes, knowledge and skills of Australian secondary teachers from schools with high numbers of ELL students. Six cases were drawn from a multiple case study investigating how teachers described their understandings about teaching ELLs, and how these understandings developed. Qualitative data were gathered using interviews and a questionnaire that prompted participants to reflect on their theories and practices relating to ELLs. These data were coded thematically, and then analysed according to Davison's (2001) conception that professional learning occurs only when dissonance disrupts a teacher's existing beliefs. Findings suggest that teachers' repertoires developed primarily through classroom experience and teachers did not readily accept professional learning outside their existing epistemology. This raises questions about how in-service and initial teacher education might generate the necessary dissonance for professional learning.