This participatory action research case study describes how one secondary school aimed to improve staff culture. Although pre-test data showed the school as performing consistently well in terms of their organisational health, the school chose to implement a line management intervention over 12 months to target three low-rating factors: appraisal and recognition, professional growth, and supportive leadership. Quantitative evaluation showed that while the improvement strategy had no effect on the intended targets, there were unanticipated effects on other factors. Staff reported a mixture of positive and negative effects from the intervention; however, a core issue was its impact on teachers' workloads. Participants reported burnout and stress as a consequence of school leaders driving continuous change. This case study argues that quality school improvement needs to be supported by a clear vision, with due consideration and attention to sustainable work practices.