* England is the only UK country to have consistently published centralised performance tables
* They were started in 1992 by John Major's Conservative government
* Labour says they're a 'non-negotiable part of reform'
* The DfES maintains it has never published 'league tables', but 'achievement and attainment tables'
* Since 2003 tables have included a 'value-added' measure to indicate the progress that pupils make during their time at school
* From next year, they will include 'contextual value-added' scores based on pupils' improvement, but adjusted to take account of social factors
* In a 2005 survey, 70 per cent of primary teachers said that league tables had a negative effect on their well-being