In this paper an investigation is undertaken into the impact and effects, on both boys and girls, of implementing single-sex classes'but particularly as a strategy for engaging boys in the English classroom at one particular Catholic coeducational school in Perth, Western Australia. Semi-structured interviews with seven English teachers at this school, where the strategy was implemented, were used both to analyse teachers' perceptions of single-sex classes in the coeducational context and to gain some insight into their pedagogical approaches. The study found that particular assumptions and knowledges about gender informed specific pedagogical approaches adopted by the teachers in single-sex English classes. These assumptions and knowledges and the way they informed the pedagogical practices of the teachers, even in the same school, varied radically. It is concluded that single-sex classes as a strategy per se do not necessarily produce enhanced social and educational outcomes for students. Rather, as indicated in the research, there needs to be more attention directed to the particular effects of pedagogy and the normalising assumptions about gender that inform the implementation of curriculum in both single-sex and coeducational classes.