This paper introduces a Gini-type index for measuring "attainment equity" in schools; that is to say, how far a school (or group of schools) is from having a "fair" proportion of its examination success attributable to a fair proportion of its student population. Using data from the National Pupil Database, the Index is applied to more than 20,000 students with matched attainment records at KS2 and KS4 in two "statistical-neighbour" local authorities in England, capturing the extent to which they are meeting a public policy notion of equity. It is then combined with existing contextual value added measures to analyse school and local authority performance in terms of both attainment equity and context. (Contains 20 notes, 4 tables, and 9 figures.)