Eleven-year-olds spend more than half of their school time learning English and maths at the expense of the other 11 subjects they should be taught, research commissioned by the exams watchdog has found.
But despite this, Bill Boyle and Joanna Bragg, of Manchester university's school of education, who carried out the research, said schools still missed the Government's targets for key stage 2.
This year, 79 per cent of 11-year-olds gained the expected level 4 in English and 76 per cent in maths. The target was 85 per cent for both. In science 87 per cent achieved level 4.
Dr Boyle compared results on the percentage of time 802 headteachers felt their school devoted to each subject every year from 1996 to 2004.
He said: "There's no doubt the focus is still intensively on English and maths. The profile of lessons hasn't changed since 2004 and it will not while the Government is focusing on these subjects."
Almost a third of time was given over to English and more than a fifth to maths at key stage 1.
At key stage 2, pupils spent more than a quarter of their time (26.7 per cent) doing English, an increase of 3.7 per cent since 1996. Maths accounted for 21.9 per cent in 2004, an increase of 2.6 per cent since the study began.
Science study decreased by 1.5 per cent at KS1 and 1.6 per cent at KS2 during this period, while subjects such as history and geography struggled to find a place in the curriculum, regularly accounting for less than 5 per cent of teaching time each.
Mr Boyle said: "Two subjects take over 50 per cent of the curriculum from 13 subjects on the menu. In no way can the Government be said to be supplying a breadth of experience for primary children in such a crucial development stage.
"The sadness to me is that the Department for Education and Skills hasn't achieved the targets it set despite skewing the curriculum so dramatically.
"The resources ploughed into maths and literacy consultants and changing whole pedagogies hasn't achieved what it wanted.
"This has been 10 years of young people's early experience of the curriculum. They've not had the chance for things like richness in art or practical geography. If you can't test it, teachers have practically been told 'What's the point?' They are made to believe that it is the first week of May that is the most important."
While the DfES did not dictate how schools planned their day, heads felt pressured to increase time spent on maths and English to meet its targets, he said.
John Bangs, head of education at the National Union of Teachers, said: "I wish the government hadn't plucked targets out of the air and obscured what is a success. Every year people compare and revisit targets but there has been a massive improvement in literacy and numeracy since 1997 and that gets forgotten."
The government intends to maintain its target of 85 per cent of 11-year-olds achieving at least level 4 in English and maths to 2008.
A spokeswoman for the Qualifications and Curriculum Authority said:
"English and maths are fundamentally important parts of the curriculum as they play an integral part in everyday life. It's important students progress through school and beyond with a strong knowledge of both."
A DfES spokesman said: "We make no apology for placing significant importance on pupils getting a solid grounding in English and maths. That is vital.
"However, we do not accept that this is at the expense of a balanced curriculum."
A curriculum without foundation by Bill Boyle and Joanna Bragg is available in the August edition of the British Educational Research Journal