England's primary schools are in danger of having a two-tier curriculum, the chief inspector of schools has said.
Ministers say they are acting already on Mr Bell's concerns
In his annual report, Ofsted chief David Bell says the quality of maths and English teaching is now noticeably better than that in other subjects.
There has been a focus on those areas in recent years because of the official literacy and numeracy strategies, though test results have hit a plateau.
The report confirms a rise in the number of schools judged to be failing.
In his report on the 2002-03 academic year, Mr Bell said other subjects supported literacy and numeracy so it was important they were taught well and not neglected.
The percentage of schools in which teaching was judged good to excellent in English and in maths was 67%, whereas the average for other subjects was 48.4%.
Mr Bell said there had been a plateau in achievement over the past four years, which concerned him. More momentum was needed.
"There is still some way to go in ensuring that all pupils in our primary schools enjoy a rich and fulfilling curriculum as well as being taught the basics of English and maths effectively," Mr Bell said.
"We cannot afford and our children do not deserve a two-tier curriculum."
The report also confirms that the number of failing schools rose last year for the first time since Labour came to power.
The number of schools judged by Ofsted to warrant "special measures" - given extra help but facing closure if they did not improve - was 515 in 1997-98.
In the last annual report it was 129. But in the period covered by this latest report it was 160, as revealed earlier this month - out of just over 3,000 full inspections during the year.
The general secretary of the Secondary Heads Association, John Dunford, said: "The increase ... may have been caused by the chief inspector saying that a 'satisfactory' judgment was no longer good enough.
"This redefinition of the word satisfactory altered the climate in which
inspectors worked and contributed to harsher judgements on school performance."
Among some "significant" gains Mr Bell highlighted "considerable improvement" in the teaching of information and communication technology in primary schools.
The government's "excellence in cities" initiative was helping schools to meet the needs of individual pupils through the use of learning mentors.
And its strategy to raise standards in the early years of secondary school was having a positive effect.
Mr Bell said it was encouraging that fewer comprehensives had unsatisfactory behaviour - but the conduct of some pupils, especially boys, "remains a serious concern for many".
"Unwillingness to listen, to concentrate and to get on with their work
continues to cause disturbance and to hinder learning," he reported.
The School Standards Minister, David Miliband, accepted the need for progress and pledged that the government's reform strategy would address Ofsted's concerns.
He said Mr Bell had identified the key areas on which the government was focusing - primary schools, ages 12 to 14, targeting underperforming schools and bad behaviour.
The leader of the NASUWT teachers' union, Eamonn O'Kane, said "the blame for the rigidity of what is taught in schools cannot be laid at the door of teachers".
"Performance league tables and the pressure they place on schools to teach to tests lie at the heart of the problem," he said.
David Hart at the National Association of Head Teachers said Mr Bell should have recognised that the funding crisis and the lack of resources in schools was a major block on progress.
"He wills the ends but does not will the means."
Conservative education spokesman Tim Collins said the report painted "a dark picture of life in some of our schools".
"It is increasingly clear that the less academic are let down by current education policies, and that the most able are being held back."
Liberal Democrat John Pugh said teachers also had a "two-tier curriculum" - trying to address the reality of the classroom and the high requests of inspectors at the same time.