In light of an international policy movement to increase focus on students' academic achievement, the question of how to improve schools has become an important issue at all levels in the school system. Substantial resources have been invested in reforms to improve conditions for pupils' learning. Great expectations and responsibility are often placed on teachers in terms of their professional development (PD), the aim being to improve their teaching practices. Consequently, the question of how to evaluate the results of school improvement programmes, including teachers' PD, has arisen. However, there is a lack of theoretical concepts that can capture the outcomes of such development in a qualified way. Taking inspiration from the research on teachers' PD and theories relating to teachers' knowledge and capabilities, the aim of this study is to outline a conceptual framework that can serve as an analytical tool when evaluating both school improvement initiatives in general and school actors' learning in particular. Four types of learning capital that are intended to reflect the central aspects of teachers' and school organisations' learning and the capabilities linked to teaching practice and its development are outlined. This conceptual framework is applied and exemplified based on the results of a 3-year research project evaluating a school improvement programme in a Swedish municipality. Finally, some conclusions are drawn regarding the different types of analysis possible with the current conceptual framework related to the evaluation of school improvement efforts.