How does changed composition of pupils affect school results?In 2012, The Swedish National Agency for Education published a study inwhich they examined how equivalence between Swedish primary schoolshas developed over time. The agency concluded that the equivalence haddeteriorated, mainly because of an increased between-school variancein results. The increased between-school variance was partly shown byexamining the increased gap between schools in which 20 % or more ofthe pupils didn’t meet the demands for passing on to secondary schooland schools where almost every pupil did. The first group has increasedsince year 2000 and consisted in 2011 of 231 schools. In this study theseschools are examined. The hypothesis that a significant change in pupilcomposition over time can explain deteriorated results is tested. The resultsshow that the schools have undergone a significant change in pupilcomposition. Mainly pupils born in Sweden by Swedish parents have leftthe schools. The majority of the schools are public schools. The changein pupil composition is strongly correlated with deteriorated results.