The school systems of many countries have been pervaded by student-centred pedagogy making students’ small group discussion a common feature of the classroom practice. However, there is a lack of studies focussing different modes of discussion for the purpose of finding out whether some modes are more beneficial than others. Hence, the aim of this study is to explore the underpinnings of student small group conversations on Socio-scientific Issues in order to develop an understanding of the key aspects of what interrupts or revitalizes the conversation. We focus on the importance of attitudes and language use for the fate of students’ decision-making conversations. Our theoretical framework builds on Dewey’s notion of Open-mindedness and Bernstein’s communication codes. Students’ use of morals, opinions and agitational talk interrupted conversations, whereas new aspects and new perspectives revitalized the conversation. Students need guidance to avoid using justifications in conjunction with a Close-minded attitude.