Examination of relationships between performance of inner-city British pupil cohorts (n=2,403, 1,479, 1,225) and their mobility among schools showed that academic performance of mobile students was substantially below the nonmobile. High mobility was strongly associated with social deprivation, family breakup, temporary housing, and refugee/migrant status. High mobility in individual schools negatively affected overall school results. (Contains 14 references.) (SK)