This article considers the role played by policy makers, government organisations, and research institutes (sometimes labelled "think tanks") in the analysis, use and reporting of PISA data for the purposes of policy advice and advocacy. It draws on the ideas of Rizvi and Lingard (Globalizing Education Policy, 2010), Bogdandy and Goldmann (Governance by Indicators/ Global Power through Quantification and Rankings, 2012) and others to explore the ways in which such "agents of change" can interpret, manipulate and disseminate the results of data arising from large scale assessment survey programs such as PISA to influence and determine political and/or educational research agendas. This article illustrates this issue by highlighting the uncertainty surrounding the PISA data that have been used by a number of prominent, high profile agents of change to defend policy directions and advice. The final section of this paper highlights the need for policy makers and their advisors to become better informed of the technical limitations of using international achievement data if such data are to be used to inform policy development and educational reforms.