Significant improvements in primary literacy and numeracy are under threat because too many lessons are no better than satisfactory, David Bell, the chief inspector, said this week.
Teaching is improving and is good or better in two-thirds of daily literacy and maths lessons, according to the Office for Standards in Education. But Mr Bell said some teachers' lack of subject knowledge was hampering progress and that further improvements in teaching were needed to build on progress made by 11-year-olds last year.
Too many teachers focused on meeting the requirements of the literacy strategy instead of tailoring lessons to pupils' needs.
Schools teach an hour of English and an hour of maths every day under the national literacy and numeracy strategies.
Literacy and numeracy results improved in 2004 after a four-year hiatus: 78 per cent of pupils reached the expected level in English and 74 per cent in maths. The Government's target for both subjects is 85 per cent.
Although more than 80 per cent of pupils reach the expected level in reading tests, two in five boys and almost a third of girls fail to do so in writing. Boys' performance in writing improved by four points in 2004 - equal to the total improvement during the previous four years.
Mr Bell said: "I am very pleased to see that, following the plateau in standards at the end of key stage 2, standards have now begun to rise. Some schools are beginning to explore greater flexibility within their curriculum."
But he was concerned that some schools do not have the confidence to stray from the strategies to offer a richer curriculum.
The report is based on visits by inspectors to 120 schools for literacy and the same number for numeracy during 2003-4. They found heads had delayed changes to the curriculum for fear they may lose recent gains made in literacy and numeracy.
Tony Halloran is head of Fonthill primary in Bristol, a 260-pupil school, which serves a deprived area and has many children with special needs. His school has been praised by inspectors as an example of good practice. Mr Halloran said: "We are still being caught out by league tables and targets.
Excellence and enjoyment is lovely, but for Year 6 you have a great chunk of time spent on booster classes so they do well in tests."