What Should an Index of School Segregation Measure?

The Centre for the Economics of Education is an independent research centre funded by the Department for Education and Skills. The views expressed in this work are those of the author and do not reflect the views of the DfES. All errors and omissions remain the authors. Executive Summary 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 socioeconomic 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 SouthEast 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 …