Children's progress is being hampered by a "stubborn core" of poor teaching, Ofsted's chief inspector of schools warned today.
While there have been improvements, there remains much in the education system that is "persistently mediocre", Christine Gilbert said.
She warned that too many young people are still leaving school without basic maths and English skills, and it is limiting their life chances.
"If children are not taught well, they will not rise above low expectations," she said.
Her fourth annual report, which covers inspections of childcare, schools and children's services in England, found that almost a third of schools are still failing to give pupils a good education.
"There is still a stubborn core of inadequate teaching," it said.
"Furthermore, too much teaching is just satisfactory and fails to inspire, challenge and extend children, young people and adult learners."
The greatest challenge now is to raise everything that is only satisfactory "to the level of good or outstanding," Ms Gilbert said.
While the report highlighted an improvement in the number of schools rated good or outstanding, one in five schools judged to be at least good last year was satisfactory or worse this year.
And almost half of the 30 academies inspected this year were not giving pupils a good education.
Ms Gilbert called for a focus on improving literacy and numeracy skills, warning that while there had been progress, it had been "slow."
And she hinted that the Government should not have scrapped its National Strategies for literacy and numeracy, without having something ready to replace them.
National Strategies were abolished by ministers this summer under a new White Paper.
Ms Gilbert said: "With the demise of National Strategies, it is vital that the importance of the acquisition of good basic skills is not diluted.
"With nearly three out of 10 11-year-olds not reaching Level 4 in both English and maths in 2009, we cannot afford to lose a focus on effective teaching."
While she said she was not asking for National Strategies to be brought back, it is "essential" there is a "national focus" to improve literacy and numeracy.
"I do not believe that just asking schools to get on with it is the answer," Ms Gilbert said.
She called for a "fundamental review" of the strengths and weaknesses of National Strategies so that lessons can be learnt from it.
While infant and primary schools were "key" in raising literacy and numeracy standards, inspectors found "weaknesses" in the way these basic skills are taught, including a lack of focus on boosting the literacy of low-achieving pupils.
Today's report also found that in a small number of primaries, pupils are being held back by their teachers' weak subject knowledge, with particular problems in maths and science.
Ms Gilbert also said she was still concerned that there was a gap in the quality of services for children from poorer backgrounds.
The quality of childcare was lower in poorer areas, and schools with a high proportion of children from disadvantaged families were more likely to be judged inadequate.
The report, which covers the academic year 2008/09, found:
:: Almost one in five (19%) schools were now rated "outstanding", while half (50%) were judged to be "good";
:: But almost a third (31%) were found to be not good enough - given a rating of "satisfactory" or "inadequate". This is fewer than last year;
:: Almost four in 10 (37%) secondary schools were rated no better than satisfactory - with 6% judged to be inadequate. The report warned that this figure was "still too high".
Ms Gilbert warned: "I see evidence of sustained improvement and I see excellence in the most difficult of circumstances.
"But across the range of Ofsted's remit, there remains too much that is mediocre and persistently so."
Shadow schools minister Nick Gibb said: "There are still far too many children being let down by the quality of education on offer. The problem of literacy in primary schools is holding back thousands of pupils, especially those from poorer backgrounds, and sows the seeds of truancy and disruptive behaviour later on."
Liberal Democrat schools spokesman David Laws said: "It is shocking that after more than 12 years of a Labour Government, nearly a third of schools are not providing a good education. This Government's failure to drive up standards in all our schools will be one of its lasting legacies.
"Ofsted was primarily established to help drive improvement in the education system, but now risks being diverted from its core purpose by the child protection agenda.
"The Government must consider whether Ofsted should be split up, with oversight of children's social services departments being hived off to a separate inspectorate."Reuse content