This chapter explores the potential of implementation science to support the development of school psychology. Implementation science perspectives and evidence base provide essential information for effective school psychology service delivery. In Scotland in particular, systems and frameworks exist in school psychology that provide a substrate for the effective incorporation of evidence-based implementations. Over the last forty years, school psychology practitioners have anticipated much of the evidence now emerging from implementation science. They have highlighted contextual barriers to change experienced in schools but arguably have lacked sufficient scientific influence and the large-scale evidential basis required to create scientific impact. Diversity in origins and scope is clearly influential in the context of the development of the role of educational psychology day to day. For school psychology, the development of realist epistemology has proved central to understanding, defining, focusing and measuring the processes which govern change in real-world contexts.