What Should an Index of School Segregation Measure? CEE DP 60

The paper aims to make a methodological contribution to the education segregation literature, providing a critique of previous measures of segregation used in the literature, as well as suggesting an alternative approach to measuring school segregation. It also provides new empirical evidence on changes in the extent of socio-economic segregation (measured by free school meals (FSM) entitlement) in English schools during the last fifteen years. Specifically, the paper examines Gorard "et al.'s" (2000a, 2003) finding that FSM segregation between schools fell significantly in the years following the 1988 Education Reform Act. Using Annual Schools Census data from 1989 to 2004, the paper challenges the magnitude of their findings, suggesting that the method used by Gorard et al. actually overstates the size of the fall in segregation by 100%. Our results show evidence of an increase in the index of dissimilarity in many Local Authorities, especially in London, although in the South-East as a whole we note that it falls. We also observe higher segregation in LEAs with higher proportions of pupils at voluntary-aided schools. We cannot confirm however, whether this is a causal relationship. It is not necessarily the case that the rise in the segregation index in these Local Authorities is attributable to the behaviour of VA schools. Much of this paper is a critique of previous methods used to measure segregation in schools. For example, we suggest that the GS index is not the optimal way of measuring changes in school segregation for the following reasons: (1) GS is not bounded by 0 and 1: the upper boundary varies according to FSM eligibility, so GS is better described as an "indicator" rather than an index of segregation; (2) GS is not symmetric, meaning that it is capable of showing that FSM segregation is rising and NONFSM segregation is falling simultaneously; and (3) GS is actually systematically variant to changes in overall FSM eligibility, except in the most stringent and unlikely of circumstances (the strict proportionate change in FSM); therefore we can properly describe it as composition variant. It had a tendency to fall as FSM eligibility rises, regardless of the change in the unevenness of school's shares of FSM and NONFSM pupils. In this paper we make the case for a segregation curve approach to measuring segregation and use one exemplar index, the index of Dissimilarity, to re-evaluate the extent of school segregation in England over the last fifteen years. What can we conclude? (1) There was no pervasive increase in segregation over the period; (2) There are a number of potential explanations for this. For example, it may be that de facto school choice did not in fact increase during this period due to capacity constraints; (3) The analysis does however provide clear evidence of an increase in segregation, as measured by the index of dissimilarity, in many Local Authorities, particularly in London. The index is also higher in LEAs with higher proportions of pupils educated at voluntary-aided schools, although this relationship is not necessarily causal; (4) We have not been able evaluate the causal impact of policies that give schools increased control over their own admissions on segregation, however we have found an association between LEAs with higher proportions of pupils in schools that control their own admissions or have explicit select by ability and the level of FSM segregation. We suggest that the level of measured segregation be carefully monitored over time, as the proportion of schools that are LEA community schools continues to fall; and (5) We note that pupil numbers in secondary schools will fall from 2005. It will be important that measures are taken to improve the ability of disadvantaged pupils to take up free places in the schools of their choice, otherwise the spare capacity in the system may well result in rising levels of segregation and in particular a concentration of disadvantaged pupils in some schools operating in deprived areas. We conclude that deciding how best to measure segregation is complex, combining fundamentally normative judgements about what exactly one intends to measure, with more technical judgements about the appropriate properties of the chosen measure. We believe that we have made a good case for a specific approach, being open about the normative judgements we have made to reach our conclusion. We have chosen to criticise one alternative approach to measuring segregation, GS, examining its properties in detail. Further research is certainly needed to subject alternative methods of measuring school segregation, such as multilevel modelling or the isolation index, to the same level of scrutiny. (Contains 6 tables, 13 figures and 12 footnotes.)