In the past two decades, scholarly discourse has consistently emphasised the efficacy of collective efforts in professional development and school improvement. Collaborative endeavours among teachers, where they systematically explore their teaching practices and collaboratively address relevant improvement issues, have proven more effective than individual pursuits in educational change. However, research also underscores the inherent challenges of such collective initiatives, particularly in collegial learning. In a longitudinal study, we adopted a pragmatic perspective to delve into the collective habits of teacher teams working towards establishing collegial learning. The identified collective habits, which revolve around collective participation, the improvement process, and scientific activities, play a pivotal role in either facilitating or hindering the establishment of collegial learning to achieve professional development and school improvement. We posit that a critical exploration of collective habits is imperative for teacher teams aiming to nurture novel and impactful practices. Strategies conducive to teachers' collegial learning encompass fostering pedagogical leadership, cultivating continuity, and embracing scientific rigour in the analysis of classroom data.