Educational disparities between indigenous Maori students and those of the majority continue to be a major issue in New Zealand. Te Kotahitanga, an iterative research and development programme, which commenced in 2001, supports teachers to implement a relationship-based pedagogy in their classrooms in order to improve Maori students' achievement in mainstream secondary schools. This article addresses the question of how gains in Maori students' achievement can be sustained and expanded. Schools, from an earlier phase of the project, in their 6th and 7th year of the programme were examined, using a theory-based model designed to evaluate and promote dimensions necessary for effective institutional support of the teaching innovation. This article demonstrates that schools that have been the most effective implementers of the intervention have seen the greatest gains made by Maori students in the 1st year of national assessments. This article then discusses effective leadership for addressing problems schools encountered while implementing the pedagogic reform.