Much has already been written on the controversies surrounding the use of different test theories in educational assessment. Other authors have noted the prevalence of classical test theory over item response theory in practice. This Special Issue draws together articles based upon work conducted on the Reliability Programme for England's examinations regulator, Office of Qualifications and Examinations Regulation. One strand of the work was methodological, in which we noted the advantages and assumptions of different approaches to investigating reliability of public examinations. A feature of the field that has not been well documented is why psychometrics in general does not always fit the educational, cultural and political priorities of...