The implementation of best practice models for assessment begins with teachers who are working in their own classes to integrate strategies into their teaching context. The effect of best practice strategies is greatly increased when there is a meeting of minds between teachers, students, school managers, academics, policy makers and, increasingly, educational consultants. This paper uses the findings of an observational case study to provide the beginnings of a baseline of information that can be used to plan for systematic evaluation of the effect of assessment innovations in classrooms and schools. It uses problem-based methodology to examine why teachers choose particular assessment practices, as well as describing what they do. This provides a useful basis for determining how professional learning should take place for real, sustainable change to be seen.