The bad teacher is experienced, not a new recruit; teaches a smaller class then her more competent colleagues; and is more likely to be found teaching nine-year-olds than five-year-olds, according to the memorandum sent to inspectors. He or she is also more likely to have trouble keeping order than to lack knowledge about the subject being taught.
The memorandum circulated within Ofsted, the standards watchdog, offers the first official picture of the profile and distribution of bad primary teachers.
Critics said yesterday that it cast doubt on government policies on both class size and improving teachers by a blitz on teacher training to boost the quality of new recruits. Gillian Shephard, the Secretary of State for Education, has cited an Ofsted study to support the Government's stance that there is no evidence that reducing class sizes raises standards.
But class size campaigners said the memo suggested that it was impossible to draw firm conclusions about class sizes when a disproportionate number of small classes were being taught by poor teachers. Christine Agambar, Ofsted's head of the research and analysis, says in the memo: "Generally, [poor teachers] teach smaller classes than their more effective peers - possibly because headteachers are anxious to place them in the best circumstances to support their effectiveness."
Her findings also throw into question ministers' belief that the root cause of bad teaching lies in trendy teacher training courses which are failing to equip teachers for the jobs.
Mrs Shephard last month announced a new national curriculum for primary teacher training. She used an Ofsted report on reading in inner London boroughs - which said that newly trained teachers were unhappy with their training - to back her decision.
The Ofsted memo says that the failings of poor teachers tend to be in their inability to keep order and to organise lessons rather than in their lack of subject knowledge, though the latter may contribute to their failings.
Reception class children and those at the top of primary schools have the best teachers, according to the analysis - just 7 per cent of their teachers are poor. Those in year five (nine and ten-year-olds) fare worst: a quarter of their teachers give consistently poor or unsatisfactory lessons. For eight-year-olds the figure is one-fifth.
Mrs Agambar says in the analysis, sent out at the end of last January, that the original figure for the number of incompetent teachers given by Chris Woodhead, the Chief Inspector of Schools, in a Panorama programme in the previous November was "a rough estimate" which had met with "justified criticism" from some inspectors.
Mr Woodhead gave a figure of 15,000 for primary and secondary teachers. Mrs Agambar's subsequent analysis for primary teachers suggests that the figure for primary is about 7000. The conclusions were based on 493 out of 20,000 primary schools, all with fewer than 9 teachers.
Ofsted said that its report, published in November 1995, said that the quality of teaching was more important than the size of the class. "If you have two classes of the same size, it is the quality of the teacher that matters," a spokeswoman said.
Margaret Tulloch of the Campaign for the Advancement of State Education said: "One has to question politicians who quote the Ofsted research since this memo seems to cast doubt on it."Reuse content