Around 600 schools have used the free, research-based Teaching, School and Leadership Practices (TSP) survey since it was first offered in 2017. This brief report is based on interviews with 10 principals who've used TSP three years in a row. The report shows the principals find it informs their own development and appraisal, identifies priorities for change, allows them to check trends over time, and whether change was happening at a sustainable pace. They used TSP reports on their own, as well as alongside other school data, particularly data about student achievement, wellbeing, and engagement. One principal described the tool as a 'one stop shop'--for principal appraisal, annual planning, and a good guide for the development of effective practices in the school.