This study investigates the sustainability and leadership of a large (more than 26 thousand members in 2023) Czech online teachers? community, the Facebook group Ucitelé+ (U+) from the onset of the COVID-19 pandemic to 2024. Drawing on digital ethnography, semi-structured interviews with three moderators and triangulating with eight active members, and content analysis of group interactions and rules, the research examines how the group developed internal governance, articulated values, and maintained engagement over time. Conceptualising U+ as a "virtual staffroom", the study identifies transformative leadership practices exercised by the group moderators, including value-driven rule-setting, content curation, and strategic moderation. The findings contribute to understanding how online professional communities can be purposefully led and sustained through adaptive, inclusive, and visionary leadership. This paper advances the theoretical notion of a virtual staffroom and highlights the relevance of transformative leadership in digital spaces, offering practical implications for the management of similar professional networks.