Social mobility in England lags behind many other developed countries, when measured by educational achievement, says an education charity's survey.
The Sutton Trust's research found children's exam results in England were more strongly linked to their parents' education than in many other countries.
But it found that this social gap was narrowing for a younger generation.
Trust chairman Sir Peter Lampl says there should be greater efforts to create a social mix in schools.
The Sutton Trust campaigns to improve the educational opportunities of disadvantaged communities.
And this research looks at the relationship between the achievements of children in school and their social background - comparing different age groups and different countries.
It found that when looking at people in England now aged in their 50s, 40s and early 20s, that the "attainment gap" between children from graduate and non-graduate parents had begun to narrow for this younger group.
However these comparisons over time are against a changing background.
The number of graduates - and children with graduate parents - has soared since the first cohort were born in the late 1950s.
Figures released in recent weeks showed that for the first time a majority of young women are now going to university.
But in terms of international comparisons, the researchers said the link between social background and school achievement remained stronger in England than in other similar countries.
"While comparable national data is only currently available for three similar countries - the USA, Germany and Australia - England emerges with the largest achievement gap for teenage children growing up today," says the research.
The researchers gave warnings about "social segregation" in England's secondary schools.
The research, carried out by John Ermisch and Emilia Del Bono from the Institute for Social and Economic Research at Essex University, describes the different intakes as the "sorting of children into higher-performing and lower-performing schools".
"We need to consider more radical options to create more balanced intakes in secondary schools and pilot innovative approaches to improve attainment for the poorest children," says the Sutton Trust chairman.
"A failure to respond to this challenge is to condemn our disadvantaged youngsters - and our economy - to the bottom of the class in education's world order," said Sir Peter.
Last year, a major report by former cabinet minister Alan Milburn warned that social mobility had slowed - and that the most sought-after professions were increasingly dominated by young people from affluent families.