The effective, sustained implementation of literacy across the curriculum in secondary schools is still a relatively rare phenomenon. This is because such an approach to literacy requires secondary schools to undergo extensive and complex processes of school change, involving altering teachers’ thinking, attitudes and behaviour in relation to literacy and pedagogy, and establishing andmaintaining organisational processes that support teachers’ change processes and their impact on student learning. Such changes take time, not least because they often run counter to traditional organisational and pedagogical approaches in secondary schools. Drawing on our research evaluation of the Secondary Schools’ Literacy Initiative (SSLI) in New Zealand, this paper examines the medium to long term implications of school change processes for secondary schools undertaking a cross-curricular literacy focus. In so doing, it identifies three key phases that secondary schools may undergo in order to achieve and sustain effective literacy practices over time and suggests that these phases, and their characteristics, may well have wider applicability.