She has rejected the recommendation of Sir Ron Dearing, her chief adviser on exams, that English coursework should be increased. In coursework, pupils are assessed on class and project work rather than final written exams.
It is the first time since her appointment that Mrs Shephard, appointed to placate teachers, has taken a decision that will infuriate them. She is thought to have had no choice because of John Major's adamant opposition to coursework.
Mr Major said three years ago that coursework in all GCSE exams should be cut to 20 per cent.
Mrs Shephard's announcement, five days after the National Union of Teachers agreed to call off its two-year test boycott, increases the likelihood of unofficial action against national tests by English teachers, who say thousands of GCSE candidates were given the wrong grades this summer because of the cut in coursework. Ministers have never before rejected the advice of Sir Ron, whose report on the national curriculum ended the test boycott.
Until last year, some English exams were all coursework. Sir Ron, who heads the School Curriculum and Assessment Authority, said the limit of 40 per cent in English should rise to 50 per cent, pointing to the "virtually unanimous support" of English teachers for coursework.
But Mrs Shephard said: "I judge that it would be premature to adjust the existing coursework limit on the evidence of only one year's examinations."
English teachers say coursework is a fairer test of ability than written exams and gives pupils a better chance of showing what they know and can do.
Anne Barnes, general secretary of the National Association for the Teaching of English, said English teachers would be ``amazed and shattered'' by the unreasonableness of the ruling.
Sir Ron also wanted to stop a cut in coursework in geography and history from 30 to 25 per cent. That was also rejected.
After members of the authority voted for changes in coursework for GCSE courses starting in 1996, officials drew up a package on coursework which they hoped would be acceptable both to Mrs Shephard and Downing Street. But, despite negotiations, they failed.
David Hart, general secretary of the National Association of Head Teachers, said the political motivation behind Mrs Shephard's decision was clear. "We should not be sacrificing the interests of our pupils to the political mood of the moment.''
But Nigel de Gruchy, general secretary of the National Association of Schoolmasters Union of Women Teachers, said it was sound education policy.Reuse content