Schools are about to be told the exam and test results they should expect to achieve given the level of deprivation of their pupils.
National benchmarks are being identified and while the Government stresses that these are not targets, parents may use them to challenge their school's results.
The Qualifications and Curriculum Authority has produced a map of the differences in attainment between schools in the leafy suburbs and those in deprived areas. More controversially, it also shows the variance between schools with roughly similar intakes.
Of the country's 15,000 primaries, around 1,100 have half or more pupils eligible for free school meals. The median score for those schools in English tests taken by seven-year-olds is about 12 per cent below the national average. The corresponding results for seven-year-olds in primaries with few pupils from disadvantaged backgrounds is more than 20 percentage points higher.
However, the data show that around 180 of schools in the highest deprivation bracket achieved at least the national average and that about 40 did as well as those in the most privileged category.
In order to deal fairly with schools that take children from widely differing backgrounds, the QCA has set benchmarks for five categories with varying proportions of children on free school meals. There is also to be a table for schools in which more than half the pupils do not have English as their first language.
Schools will be told the range of scores in English, maths and science achieved in their category and their national benchmark will be the level achieved by the best 25 per cent. In total, there will around 30 national benchmarks for primaries and more for secondaries.
The information for secondaries will show the range of scores achieved by selective schools, secondary moderns and six categories based on varying proportions of the intake eligible for free school meals. The tables are expected to show that the attainment gap between schools widens at secondary level.
According to David Hawker, head of curriculum and assessment at the QCA, schools are to be provided with a sophisticated indicator system to help them set targets in liaison with education authorities.
There is little research on the extent to which schools already set targets - though Birmingham is one of a number of authorities that has been encouraging it - and they do not have to publish targets for parents for another a year.
Officials at the Department for Education and Employment say that schools will not be required to set the national benchmark as their target, but will be advised to make a realistic estimate of their progress. Parents, however, may ask why their child's school is not aiming to do as well as similar schools.
The fears of the teacher unions are that schools will feel forced to concentrate on English, maths and science (the legal requirement is for targets in the core subjects).
The National Union of Teachers has said that the intense pressure on local authorities to lever up standards could result in too many targets, or over-ambitious ones, being imposed on particular schools.
In addition, it warned that many local education authorities lack the expertise and staff to support under-performing schools.
The Government accepts that requiring schools merely to set targets will have not raise standards - for which schools need to have a strategy. The literacy hour and more prescription in maths will impose part of the strategy, but schools that are far below their benchmark will need additional help.
Benchmarking could put greater pressure on schools than performance tables, because schools cannot complain that they are being compared against others in more favoured areas.
Performance tables, centre pages