This article describes the empirical research that contributed to the development of the model of "effective school improvement". The focus is mainly on the findings of that research but the problematic nature of designing a methodology that is applicable in 8 very different education systems is also discussed. The 4 key factors to emerge from the research were the importance of context, the role of external changes agents, the importance of internal change agency, and the complexity of the relationship between all the factors and influences. These factors and their contribution to the emerging ESI model are discussed in relation to the theoretical reflections reported in the previous article. (Contains 2 tables.)