Schools are unlikely to hit the Government's English target for 14-year-olds, the chief inspector warned this week.
The key stage 3 strategy has improved teaching in all the core subjects but low-attaining 11 to 14-year-olds should get more help, according to a report by the Office for Standards in Education.
Standards have improved in most schools but more needs to be done to promote literacy and numeracy across the curriculum.
The KS3 strategy has also failed to ensure a smooth transition for pupils between primary and secondary schools - a key aim.
Ofsted's evaluation of the third year of the strategy found that it is improving the results of high-flyers but less able pupils are being left behind.
Catch-up classes for those who struggled with maths in primary school are failing to bring pupils up to the expected standard.
In English, many low achievers still have significant problems with their writing. "Weaknesses in reading and writing continue to be a major handicap for too many pupils in their work across subjects," the report says.
Pupils of all abilities are being held back because they are being asked to repeat parts of the curriculum already studied at primary level. The arrangements for pupils moving from primary to secondary school are unsatisfactory in one in six schools. In half, the continuity of the primary and secondary curricula was weak.
Chief inspector David Bell said: "There is still much to do to enable more pupils to make good progress from the start of their secondary education."
By 2004, the Government expects 75 per cent of pupils to reach the required level in English and maths and 70 per cent to achieve the level in science.
Last year, the proportions reaching those levels were 69 per cent, 71 per cent and 68 per cent respectively.
Pupils' progress in maths has been held back by recruitment difficulties, inspectors said. Staffing was unsatisfactory in three out of 10 schools visited and low-attaining classes are more likely to be taught by non-specialist teachers.
"The targets for mathematics and science are within reach, but the English target is challenging, given the present rate of progress," the report says.
Inspectors found that the strategy is adding greater purpose and challenge to many lessons. It has also had a positive effect on pupils' attitudes, particularly boys' in English lessons.
The report says measures should be taken to improve the quality of assessment in all subjects and to ensure greater continuity between primary and secondary schools.
Ofsted also calls on schools and LEAs to improve the management of the strategy and make better arrangements for monitoring and evaluating its impact. Currently, one in six KS3 managers is judged to be ineffective.
David Miliband, the schools minister, said that the Government would introduce measures to address Ofsted's criticisms. "The priority now is to build on the significant progress we have already made and translate this into even greater gains," he said. But he noted that the 2003 results were the best on record.
Eamonn O'Kane, general secretary of the National Association of Schoolmasters Union of Women Teachers, said that Ofsted's recommendations could significantly increase the bureaucratic burdens on teachers.
Tim Yeo, shadow education secretary, promised to scrap the targets:
"Despite spending hundreds of millions of pounds of taxpayers' hard-earned money, Labour is still leaving thousands of children behind," he said.
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