This paper examines the role of professionalism in teachers' change in practice related to dialogue and argumentation. Data were collected from 14 pre-primary and primary school teachers who participated in a professional development programme with an emphasis on promoting values such as tolerance, empathy, inclusion and social responsibility through dialogue and argumentation. Data from teachers' transcribed lessons revealed discrepancies in teachers' implementation of the lesson plans, despite receiving the same professional support. This paper argues that the discrepancies lie in the notion of professionalism, accounting for teacher agency, self-efficacy and autonomy. Three positions on the professionalism continuum were identified from this implementation: the prescriber, the implementer and the enactor. Interview data examining teacher professionalism traits confirmed these positions. The paper aims to contribute to the literature on professionalism, as the latter re-emerges as a key concept in recent teacher professional development literature.