Purpose: The purpose of this paper is to examine how teachers engaged in curriculum deliberation through lesson study (LS) and how different types of teacher knowledge were elicited, co-constructed and transformed in integrated ways across LS stages. It also clarifies how different school-level orientations influence the nature, depth and scope of the deliberation. Design/methodology/approach: The study adopted an interpretive qualitative case study approach involving two schools, employing participant observations of LS cycles and post-LS teacher interviews. Thematic analysis and analytical coding were conducted. Findings: The two cases revealed core features of curriculum deliberation trajectories enabled by LS: problem identification, planning to unlock the educative potential of content and reflection on enactment for improvement. The types of teacher knowledge that informed deliberation on English language learning were uncovered to reveal LS teams' initial comprehension, collective reasoning and actions, and new knowledge derived. Pedagogical content knowledge was prominently drawn on in unlocking curriculum potential and transformed with the knowledge of student learning gained from the live lesson observations. The school-level orientations were found to influence the extent to which teachers can interrogate existing practices and co-construct knowledge. Originality/value: The study offers a nuanced understanding of curriculum thinking in LS teams, which is enabled by processes that construct the dialogic space for coordinating curriculum commonplaces to transform content into pedagogical representations to cultivate students' future capacities. It highlights the importance of viewing sustainable LS from an interconnected perspective that calls attention to the social contexts of deliberation.