The data will allow parents to track their child's academic performance and compare it with that of other pupils in the same school and across the country. Teachers will also be able to see how well their classes are doing against others and show how well groups of pupils - for example, ethnic minority children or 13-year-old boys - are performing.
In one of the biggest changes to the analysis of performance since the introduction of league tables in 1993, it is the first time such information will be made available anywhere in the world. Mr Miliband says the information will allow teachers to tailor lessons to individual children rather than offer a 'one size fits all' service. Whitehall sources admitted it sounded the death knell for 'standard' comprehensive education, in which every pupil receives a similar type of teaching.
The new data is based on 'value added', the improvement made by pupils between 11 and 16, taking into account prior attainment, poverty and gender. It challenges the combination of lack of expectation and the culture of quiet underachievement that can hold back pupil progress. It poses as many questions for 'coasting schools' in leafy suburbs as for those in inner cities.
The new computer data is likely to reveal that many inner-city schools have improved enormously since 1997 but that many schools in more comfortable suburban areas are not doing enough. The 'mosy improving' school in England is in Tower Hamlets, a deprived inner borough in east London.
The project is called Assessment for Learning and, controversially, will allow headteachers to pinpoint teachers whose classes are not performing as well as others. Failing teachers could eventually be sacked if they are unable to improve.
Every parent should be able to demand 'tailor-made teaching' for their own child, Mr Miliband argued. At present only 40% of schools were using Assessment for Learning techniques to improve performance. 'This is a reform that should animate every secondary school,' he said.