School Effects

How Unstable are ‘School Effects’ Assessed by a Value-Added Technique?

Stephen Gorard, Rita Hordosy, Nadia Siddiqui


This paper re-considers the widespread use of value-added approaches to estimate school ‘effects’, and shows the results to be very unstable over time. The paper uses as an example the contextualised value-added scores of all secondary schools in England. The study asks how many schools with at least 99% of their pupils included in the VA calculations, and with data for all years, had VA measures that were clearly positive for five years. The answer is – none. Whatever it is that VA is measuring, if it is measuring anything at all, it is not a consistent characteristic of schools. To find no schools with five successive years of positive VA means that parents could not use it as a way of judging how well their primary age children would do at age 16 in their future secondary school. Contextualised value-added (CVA) is used here for the calculations because there is good data covering five years that allows judgement of its consistency as a purported school characteristic. However, what is true of CVA is almost certainly true of VA approaches more generally, whether for schools, colleges, departments or individual teachers, in England and everywhere else. Until their problems have been resolved by further development to handle missing and erroneous data, value-added models should not be used in practice. Commentators, policy-makers, educators and families need to be warned. If value-added scores are as meaningless as they appear to be, there is a serious ethical issue wherever they have been or continue to be used to reward and punish schools or make policy decisions.

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To cite this article: Gorard, S., Hordosy, R. and Siddiqui, N. (2013) How stable are ‘school effects’ assessed by a value-added technique?, International Education Studies, 6: 1, 1-9,


Does the index of segregation matter? The composition of secondary schools in England since 1996

Stephen Gorard


This paper presents a new analysis of segregation between schools in terms of pupils living in poverty, for all secondary schools in England from 1996 to 2005. This shows that the clustering of similar pupils in specific schools increased noticeably from 1996 to 2001, but then settled at a level still below that of 1989 when official records began. The analysis uses four estimates of segregation using figures for take-up of, and eligibility for, free school meals compiled to create both the dissimilarity index and what has been termed the Gorard index of segregation. All four estimates give the same substantive results and the findings for the dissimilarity index and the Gorard index of segregation using either measure of free school meals are indistinguishable. The two indices are, therefore, measuring the same thing. However, the Gorard index of segregation is again shown to be more tolerant of the precise measure being used and so more strongly composition invariant than the dissimilarity index. This has important implications both for the past debate on how to measure segregation between schools and for how education authorities go about estimating segregation in the future.

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To cite this article:Gorard, S. (2009) Does the index of segregation matter? The composition of secondary schools in England since 1996, British Educational Research Journal, 35: 4, 639-652

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