England's brightest pupils have fallen two years behind in maths compared to international counterparts in places such as Taiwan and Hong Kong by the time they reach 16, according to a new report.
A study by the University of London's Institute of Education found that at the age of 10, England's highest achievers are at the same level as those in East Asia, but by age 16 they have lagged behind.
In fact they had made less progress than pupils from all of the 12 other countries in the study including Russia, the US, Japan and Scotland.
Researchers looked at achievements in two respected international studies of attainment - the Programme for International Student Assessment (PISA) and the Trends in Mathematics and Science Study (TIMSS) .
They analysed the results of the TIMSS tests taken at age 9/10 (in 2003) and 13/14 (2007) as well as the PISA test for pupils aged 15/16 (2009).
One of the report authors, Dr John Jerrim, suggested that grades could be improved by focusing more on maths in primary school.
He said: "That's not to say there’s nothing that can be done during secondary school.
"There's probably some sensible things going on at the moment with reforming the secondary curriculum to stretch the highest achievers more."
Aside from the top 10% of pupils, the study found that overall the nation's pupils are already behind those in east Asia at age 10, but this gap does not widen between then and 16.
In response to the results, Education Minister Elizabeth Truss said: "This Government is clearing up Labour's mess.
"Our reforms - tougher discipline, more rigorous exams, more freedom for headteachers, a more demanding curriculum and higher quality teaching - will drive up standards so our pupils have a first-class education that matches the best in the world."