Student wellbeing is recognised as a critical factor in supporting learning outcomes. However, when teachers are assigned expanded roles as mentors to monitor and support wellbeing, they often lack the necessary support to fulfil these responsibilities effectively. This study explores the tensions and behaviours that arise when teachers implement a novel wellbeing tool designed to provide insights into students’ wellbeing. Adopting a mixed-methods approach, data were gathered through a survey and interviews with teachers (n = 39) and analysed through the lenses of Activity Theory (AT) and the Theory of Planned Behaviour (TPB). The findings reveal that integrating the wellbeing tool introduced new practices, resulting in primary and secondary tensions concerning roles, implementation, and use. The integration of TPB uncovered psychological factors influencing teachers’ intentions and behaviours, complementing the systemic insights from AT. The study contributes to the broader conversation on enhancing educational practices to support student wellbeing, fundamental to achieving positive learning outcomes.