This study focuses on an intervention programme designed to foster collectivity in classroom dialogue during sixth-grade language arts lessons, incorporating a coaching-based approach grounded in real classroom experiences. Specifically, we examine how this programme affected the beliefs and practices of a sceptical teacher in relation to increasing the participation of all her students in the classroom discourse. Centred on a case study of one teacher, the research uses multiple data sources, including video-recorded lessons and reflective interviews. The analytical approach is interpretative, taking into account the role of the researcher in influencing the observed phenomena. The intervention involved a video-stimulated reflection on a lesson leading to an impasse because the teacher could not work with all of the students due to her deficit beliefs about the students. In our analysis, a distinctive cyclical model encompassing six steps was introduced to delineate the evolution of the teacher's beliefs. This model emphasises the crucial role a researcher plays in teacher learning, particularly in providing emotional support and aiding in the collaborative construction of teaching methodologies. Video recordings combined with 'reflexive noticing' made it possible for the teacher to recognise alternative interpretations of silent student interactions, thus challenging the previous deficit models. Recognising an impasse -- an emotionally intense point of confusion -- is essential in the process of belief alteration. The research suggests that while reflection is important, it alone is not sufficient; genuine change arises from teachers' efforts to address and navigate confusion and impasse in their practices.