The TESSA (teacher education in sub Saharan Africa) programme aims to improve teacher education at scale by developing open educational resources (OER) that allow sustainable and locally managed pedagogical change in higher education institutions and schools. The article offers a sociocultural theoretical rationale for the pedagogy of mutuality represented in the TESSA OER; and for the research approach to understanding pedagogical change that recognises the dialectical relationships between national policies and institutional structures and practices, and the consequent impact of these on teachers' practice and pupils' learning. It reports from an interview-based enquiry, from the project "Extending and embedding TESSA OER", looking at how teacher educators at a Kenyan University served to broker changes in pedagogy within the institution and its partner schools. Two school-based cases are discussed that highlight the role teachers, who take up these pedagogical challenges play in further brokering change in their local institutions; some of the influences that support the process of institutional change are identified and how these are understood and reported to increase access and enhance learning for all pupils. (Contains 1 figure.)