This report covers children's progress during Key Stage 2 in all primary schools in England over a three year period (2002-2004). Value added multilevel models are used to investigate children's progress in Key Stage 2 by controlling for prior attainment, as well as several background influences. These analyses allow measurement of the extent to which children's progress can be attributed to the primary school attended. Primary schools where children make significantly greater progress than predicted (on the basis of prior attainment and intake characteristics) can be viewed as more effective and schools where children make less progress than predicted can be viewed as less effective. The phrase effectiveness throughout this report refers to this measure of progress, not to any other characteristics or qualities of schools.