UK primary and secondary teachers are raising pupil performance levels, according to new international tables, but inequalities continue to affect the country's schools.
Rankings published by the Organisation for Economic Cooperation and Development (OECD) indicated that UK results were above average, but that it did less well in a comparison of teenagers' reading skills with levels of social equity.
It was one of several countries, which also included the US, France and Germany, where fairness levels lagged behind overall pupil performance.
By contrast, Shanghai, Finland, South Korea, Canada, Japan, Hong Kong and the Netherlands featured among school systems with both high pupil results and equity.
Russia, Spain, Croatia and the Czech Republic did well on equity but not on results, while Bulgaria, Turkey and Kyrgyzstan fared poorly on both.
Andreas Schleicher, the OECD's special adviser on education, remarked that social polarisation had long been a problem within the UK's education system, although there had been some recent improvement.
He told BBC News that this was an issue facing other major western economies as well and that the challenge for these states is to develop an education system in which widespread underachievement by poorer children is no longer seen as acceptable.
Mr Schleicher stated: "In the past, economies and school systems could tolerate these inequalities.
"But the life chances are deteriorating rapidly for those without qualifications. There are more severe penalties."
Commenting on the OECD report, a Department for Education source told the BBC that it was based on data from 2009 and highlighted how the previous Labour government had failed the UK's poorest children.
The spokesperson listed steps taken by the current government to reduce pupil inequality, such as tackling underperforming schools and introducing the pupil premium, which targets funding at the poorest children.
Yet Labour education spokesperson Stephen Twigg said the government was going in "the wrong direction", pointing to recent falls in the number of young people staying in education and in the number of children getting catch up tuition as evidence of this.
Meanwhile, Christine Blower, general secretary of the National Union of Teachers, said pupils' socioeconomic disadvantage can be overcome if schools have sufficient resources available to guarantee high quality, consistent educational provision.
She claimed this was being hindered by school budget cuts, which pupil premiums were not enough to offset, while the academies and free schools programme was further "fragmenting the education landscape".
Posted by Harriet McGowan