This presentation focuses on principals practicing within Swedish municipal adult education,MAE, and their understanding of leading education based on scientific foundation and proven experience, and reports on a study in a research project that was initiated in 2019 in collaboration between a researcher and two practitioners within MAE. The initiation of the research project is a response to challenges in terms of quality within Swedish MAE and to the call for school improvement research on the topic.The research project aims to explore leadership and school improvement within Swedish local MAE in relation to individuals’ right to public education. Our research collaboration was set up with an action research approach and the research project evolved over time, using multiple methods of data collection and analysis. The interest of this particular study stemmed from the findings from our previous studies within the project, in which principals practices of leading and organization were viewed as weak from a teacher perspective. The context includes a Swedish reform from 2010 when a legal act was implemented regulating that all education in Sweden shall be based on scientific foundation and proven experience (SFS2010:800). The underlying assumption behind the act has been that education based on scientific foundation and proven experience would professionalize practitioners and thereby improve quality and efficiency in the internal processes of schools and increase student achievements. The study in this article returns to previously studied local MAE, interviewing the principals about their understanding of leading school improvement based on scientific foundation and proven experience to provide additional perspectives on studied local MAE.  The purpose of this article is to explore MAE principals’ understanding of what it means to lead education based on scientific foundation and proven experience and its implications for their leadership practice. Research questions are; What variations in the understanding of educational leadership, based on scientific foundation and proven experience, are there among principals, and how do those variations in understanding influence principals’ leading practice? In what way are they interrelated? A phenomenographic theoretical framework and methodology is applied. Data is comprised by ten interviews with MAE principals.Phenomenographic analysis results in four categories of principals’ understandings of enacting the 2010 act. The inter-relatedness between the categories forms a hierarchical structure, an ananatomy of understanding that shape leading practice, that moves from an instrumental understanding and practice towards more complex forms. The anatomy of principals’ understandings is constituted by qualitative and interrelated mental structures that illustrate principals’ development of their understanding of what it means to lead education based on scientific foundation and proven experience. Results are discussed in terms of representation and context, and also in relation to the research field. Moreover, the implications of the results for quality in MAE are discussed.