Some implications of choice of tiering model in GCSE mathematics for inferences about what students know and can do.

This study compared models of assessment structure for achieving differentiation across the range of examinee attainment in the General Certificate of Secondary Education (GCSE) examination taken by 16-year-olds in England. The focus was on the “adjacent levels” model, where papers are targeted at three specific non-overlapping ranges of grades. Examinees enter for a pair of papers at adjacent levels and receive the highest grade achieved. There is no aggregation of marks across papers. This study used simulation, based on data from a GCSE Mathematics exam, to compare the adjacent levels model with two other tiering models in terms of: (1) suitability of grade boundary locations; (2) score distributions; and (3) reliability. The adjacent levels model led to lower reliability but arguably improved two aspects of validity: the strength of the inference about what examinees with a given grade would know and be able to do; and the removal of the ambiguity about overlapping grades inherent in the current system. [ABSTRACT FROM PUBLISHER]