Mathematics Teachers in Collaboration: A Commentary

Having read all the chapters in the volume “Teachers of mathematics working and learning in collaborative groups” based on ICMI Study 25, I can summarise my reaction in a few words: I am overwhelmed. As chapters that report the activity of the working groups already summarise and analyse the studies in the submissions, I find it useless to position my commentary as a ‘summary of summaries’ or an ‘analysis of analyses’. As such, my ‘commentary’ is a set of comments, my personal reflection on what I noticed, what I wondered about and what attracted my attention when reading the chapters.