PREP school pupils are surging well ahead of national norms, Richard Tovey, chairman of the Incorporated Association of Preparatory Schools, said on Tuesday.
Half of the 11-year-olds in prep schools who took key stage 2 tests this year achieved the level expected of 14-year-olds, he told the association's annual conference in Eastbourne.
These results showed graphically how much progress pupils made with the benefit of "a demanding and flexible prep- school education," he said.
The level 5 results obtained by 11-year-olds had improved by at least nine points compared with 1998 and science by 14 points, from 36 to 50 per cent.
Overall, 93 per cent of the 5,000 prep pupils who took the tests this year reached level 4, the expected standard for 11-year-olds, in each subject, with 96 per cent reaching it in science. The national average results, released last week, show that 70 per cent reach level 4 in English and 69 per cent in maths.
Prep schools do not have to take part in the tests but about 150 schools - nearly a third of IAPS members - do.
Mr Tovey stressed that high scores in English, maths and science were not the whole story. Prep schools were also able to offer spiritual teaching, moral and sporting openings and creative arts.
Mr Tovey, whose school, Tockington Manor, Bristol, is involved in a partnership scheme with local primary schools, urged members to seek new ways of co-operating with state schools. "What a joy it is to be encouraged to work with others...rather than expending energy on fighting for one's right to exist," he said.
Partnerships between state and private sectors were also praised by school standards minister Estelle Morris who launched new guidance at the conference on how the best examples work.
Independent schools would soon be invited to apply for grants totalling pound;400,000 to run partnerships.
The guidance includes examples such as the maths-teaching link between James Allen's prep school and Southwark's Charles Dickens school, under special measures.