In recent decades, there has been a growing body of research that highlights local education authorities (LEA) as potential contributors to support school capacity building and result development. Despite this, there are few empirical studies that have explored what effects different strategies and policy actions from the LEAs actual have over time. Based on results from a five-year research project in a major Swedish municipality, the aim with this multiyear and multi-level study is to explore the effects of a LEA’s quality management processes of six schools’ capacity building. The results from the study show a clear strengthening of the schools’ improvement agenda, improvement organization and improvement leadership of the six schools. Two LEA strategies can be distinguished as especially important to explain the school improvements: i) systematic and long-term data-based school improvement routines and processes; ii) quality dialogues for monitoring and support. Two conclusions can be drawn: i) the importance for the LEA to be responsive so its improvement strategies are integrated into the schools’ local school improvement system; ii) the importance that the LEA work with multifaceted strategies containing aspects of control and accountability and learning and support.