Background: Teachers’ limiting conceptualizations of students influence students’ learning opportunities. We analyze teachers’ professional conversations to understand how dialogues can expand teachers’ conceptualizations. Methods: We examine professional dialogues from 9 whole-school intervention meetings. Drawing on discursive psychology and activity theoretical notions of learning the study conceptualizes teachers’ collective assumptions as a lived ideology actively sustained by stabilization discourses. We analyze the discursive devices through which the teachers’ talk about their students limits/expands their sense of what is possible in their teaching and their dialogic effects. Findings: Our analysis finds a range of discursive strategies that sustain or restabilize the lived ideology. Even when challenged by contrary evidence (e.g., surprises), dilemmatic tensions and reframing repair actions are found to close potential dialogic openings. Importantly, we identify a form of discourse that avoids immediate closure, characterized by sustained reflection on the students’ challenges developing a need to change. We term this reflexive noticing: it is enabled through sustained puzzle, constructing dilemmas as origin of change and discursive consciousness of stabilization. Contribution: We illustrate why contrary evidence often fails to shift limiting conceptualizations about students and show the discursive mechanisms generating possibility knowledge (Engeström, 2007). Implications for teacher learning are discussed.