Collective approaches to practice development are increasingly common in the teaching profession. Such initiatives frequently involve groups of teachers taking responsibility for introducing, sharing and developing new pedagogical resources and for aiding their integration into existing practices. This article explores teachers' knowledge work as a component of collective practice development, and investigates how engagement with knowledge is constructed in different school environments. Drawing on research that followed an Assessment for Learning (AfL) project in a Norwegian city, the article examines how two groups of lower secondary teachers worked to support the introduction and development of AfL resources at their respective schools. The analysis reveals how their knowledge work was framed in different ways through available organisational roles and resources, and discusses the implications for initiatives aimed at collective practice development at the school level.