Pupils will be able to score up to 75 per cent on the new science GCSEs by choosing answer A, B, C or D, from November.
They will sit six multiple-choice papers of either 20 or 30 minutes, each of which is being offered with up to five resits and is computer-marked.
The exam, offered by the AQA and Edexcel boards, is the first major GCSE to be mainly multiple choice.
The rest of the qualification is a new type of coursework, in which pupils will also get up to six attempts to achieve a good mark.
Edexcel's website boasts that the new exams give students "more chances to succeed", saying that they can be tested "at any time, allowing them to be tested on material when it's fresh, and can take multiple tests".
Pupils taking Edexcel will also be able to score up to 10 per cent on the basis of teacher marks, which the board will usually not check.
The exams, which are also the first mainstream GCSEs to give pupils the chance to take some modules by computer, are provoking intense controversy.
Derek Bell, chief executive of the Association for Science Education, said: "This seems to be an over-simplistic way of assessing what is a very complex learning process."
Jonathan Osborne, professor of science education at King's College, London, said he was surprised the new exams had been approved by the Qualifications and Curriculum Authority (QCA).
He said: "How is this going to assess pupils' ability to express themselves using scientific language, which is a major aspect of science?"
Critics argue that the new GCSEs have been designed to be easy to mark and to make it simple for pupils to get top grades. The boards say that multiple-choice, or "objective tests", can be a good check on understanding.
The development will heighten the controversy over GCSEs and A-levels.
Anthony Seldon, master of Wellington College, writes in today's TES that confidence in the system is "draining quicker than credibility in George W Bush's stance on Iraq".
Mr Seldon is organising a conference in three weeks in which private heads will debate alternatives to mainstream exams.
The new core science GCSEs are part of a set of courses designed to make the subject more exciting. Subjects covered include genetic engineering, global warming and nanotechnology.
Most pupils will take them alongside a second GCSE, in additional science, which is being assessed more traditionally.
For coursework, pupils will complete up to six unassessed investigations.
Their teacher will then set them board-designed tests on each project, in exam conditions. The best mark will count towards their grade.
An AQA spokeswoman said: "The variety of assessment processes we use reflects the diversity of skills being tested across a wide range of subjects. All our specifications have been subject to QCA accreditation procedures."
An Edexcel spokeswoman said its new courses were designed by science teachers and accredited by the QCA.
A QCA spokesman said the new specifications had yet to receive final accreditation, because the regulator believed that example questions suggested by the boards were not sufficiently "rigorous".
But he added that the concept of multiple-choice exams was something that the QCA was happy with.
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