The Government says the tests, which will take four and a half hours and be completed under examination conditions, are not a return to the 11-plus which children either passed or failed.
A spokesman for the Department for Education said they were designed primarily to assess pupils' progress and to place them in one of the ten levels of the national curriculum. 'If some schools also choose to make use of them for selection, that is up to them,' he added.
Next summer's tests will be a trial run but Mr Patten expects that 80 per cent of primary schools will take part. The tests will be compulsory for all 11-year-olds in 1994. Their design will reflect ministers' determination to limit teacher assessments and practical tests. Teachers argue that they are not a fair test.
The School Examinations and Assessment Council, which advises the Government on exams, will invite groups to develop tests which will focus on the basics of reading, writing, spelling and arithmetic. More time will be given to English than to maths or science.
There will be three tiers of difficulty and teachers will decide which papers pupils will sit. The average 11-year-old will reach level 4 and the top paper will be for children who have reached levels 5 or 6.
Mr Patten said: 'I am determined to ensure that the tests for 11- year-olds are rigorous and rewarding . . . Sensible testing of pupils is essential to inform teachers, parents and pupils about how well children are doing at school by highlighting both strengths and weakness, showing where help is needed.'
He believed 11-year-olds, like 14- year-olds who took pilot tests this summer, would take the new tests in their stride.
The tests will probably take place in the week beginning 17 May and be marked by teachers. They will concentrate on knowledge and understanding, leaving teachers to assess practical skills in the classroom.
Jack Straw, Labour's education spokesman, said ministers were opening a can of worms by suggesting schools could use the tests for selection. Most children would have been allocated a secondary school place before they took the tests so they could only be used in late appeals.
Peter Smith, general secretary of the Assistant Masters and Mistresses Association, said: 'The Government must explain more fully as to whether it sees this form of tests as a means to return to the old, discredited system of 11-plus selection. No one, least of all parents, is going to be happy if the tests are all paper and pencil. A teacher's overall assessment of a pupil is vitally important if a balanced picture of a child's ability is to be obtained.'
Doug McAvoy, general secretary of the National Union of Teachers, said: 'Teachers will end up teaching to the tests and simply getting children to regurgitate facts.'
Tests for 11-year-olds are also being commissioned in technology, history and geography. Teachers will be able to use them in assessing pupils. Assessment will be compulsory in technology from 1994; in history and geography from 1995.Reuse content