This article describes two collaborative research projects whose common goal was to explore the potential role of professional controversies in building teachers' summative assessment capacity. In the first project, upper primary teachers were encouraged to compare their practices through a form of social moderation, without prior instructor input or theoretical preparation. In the second project, lower secondary school teachers were encouraged to compare their summative assessment practices with reference to a theoretical model of curriculum alignment, under the guidance of an instructor. The findings support the potentially constructive role of professional controversies in supporting teachers' professional development for summative assessment. They highlight the status of references called upon in discussion of controversies, and their contribution to the construction of the subjects under discussion.