text: I found some articles and studies on the subject.\n\nMIXED ABILITY CLASSES REDUCE INDIVIDUAL PERFORMANCE\nhttp://www.warwick.ac.uk/res2003/media/fertig.html\n\nSuccess of mixed ability classes depends on what you teach\nhttp://ioewebserver.ioe.ac.uk/ioe/cms/get.asp?cid=4578&4578_0=3424\n\n"In secondary schools, Students’ experiences of ability grouping similarly suggests that setting in mathematics has a negative effect on both attainment and motivation, with the exception of slightly improved attainment for top set pupils." http://www.standards.dfes.gov.uk/research/themes/pupil_grouping/\n\n“Tell me with Whom You’re Learning, and I’ll Tell You What You’ve Learned: Mixed Ability Versus Same-Ability Grouping in Mathematics ”  http://www.mste.uiuc.edu/courses/ci399ATGfa02/folders/mstoraasli/ci399_article_2.htm