Where children grow up in England is more likely to determine success or failure at school than in previous generations, a study suggests.
The Social Market Foundation has examined test results of cohorts born in 1970 and 2000 and found regional differences have become much greater.
Pupils' results are highest in London and lowest in Yorkshire and Humber.
"Where you live has become much more important," said think tank director Emran Mian.
The comparisons between the generations, based on school tests in primary school and exams such as O-levels and GCSEs, indicate that geography has become a much more significant factor in how high pupils are likely to achieve.
For pupils born in 1970, the study says that location was much less of an influence, with a much a stronger link to factors such as social background.
Family background and income remain important, but the study says "the geographic area a child comes from has become a more powerful predictive factor".
The rise of London schools has been a key part of this, with some of the poorest areas of the country achieving relatively high results.
In the mid-1980s, areas such as the south-east and east of England had better results than London, but the most recent results show London outstripping the rest of the country.
This prompted Ofsted chief Sir Michael Wilshaw to warn of a "North-South divide" in schools. There were also concerns about coastal towns becoming pockets of underachievement.
How different parts of the country compared in GCSE results for 2014:
The study from the Social Market Foundation suggests the achievement gap between the richest and the poorest pupils remains "persistently large".
And the gender gap has grown wider, with girls even more likely to achieve higher results.
There has been a substantial shift in the achievement of ethnic minority pupils.
For those born in 1970, who took O-levels in 1985-86, black and Asian pupils' results were considerably below average and behind their white counterparts.
The GCSE results for 2013-14 show a much more complex picture.
The black and Asian categories, broken down in more precise ethnic groups, indicated Indian pupils' results were above average, while Pakistani pupils were below average. Black African pupils were above average and black Caribbean were below.
White pupils were below average, with the weakest results from poor, white boys.
But Dr Alice Sullivan, director of the 1970 British Cohort Study, Centre for Longitudinal Studies, at the UCL Institute of Education, said that the numbers of ethnic minority pupils born in 1970 were too small to make such comparisons.
The Social Market Foundation is setting up a commission on inequalities in educational achievement, which will be chaired by Nick Clegg, the former leader of the Liberal Democrats.
"While parental income remains very important, this new research shows that where you live has become a much more important factor in determining educational achievement," said Mr Mian, director of the Social Market Foundation.
"Our new research also shows that the story around ethnic origin and education has become much more complex."
Professor Stephen Gorard, from Durham University's school of education, said it was wrong to attribute the differences in achievement to "the impact of location rather than pupil background".
He highlighted higher levels of poverty in areas such as the north east and midlands.
A Department for Education spokeswoman said: "In a recent report the Public Accounts Committee found the attainment gap between disadvantaged pupils and their peers has fallen at both primary and secondary level.
"However we recognise that there is more to do - we are expanding the Teach First and Schools Direct programmes and launching the National Teaching Service, which will mean more great teachers in schools in every corner of the country, so that we can extend opportunity to every single child and ensure all schools can recruit the teachers they need.
"The pupil premium, worth £2.5bn this year, is providing vital support to disadvantaged children and helping ensure every child, regardless of their background, is given the opportunity to fulfil their potential."