Within the segregation literature there has been a movement away from measuring ethnic segregation at a single scale, using traditional indices, to instead treating segregation as a multiscale phenomenon about which measurement at a range of scales will shed knowledge. Amongst the contributions, several authors have promoted multilevel modelling as a way of looking at segregation at multiple scales of a geographical hierarchy, estimating the micro‐, meso‐ and macro‐effects of segregation simultaneously. This paper takes the approach forward by outlining a multilevel index of dissimilarity that combines the advantages of using a widely understood index with a means to identify scale effects in a way that is computationally fast to estimate with freely available software to do so. To demonstrate the method, a case study is made looking at the residential separation of White British pupils from six other ethnic groups in England in 2011. It examines a claim made by the Casey Review into opportunity and integration that schoolchildren are more residentially segregated than the population at large. The results suggest that schoolchildren were indeed more residentially divided but comparison with earlier data and the general uplift in the scales at which patterns of segregation are evident suggest a trend of decreasing segregation overall and the spreading out of ‘minority’ groups.