Prep schools were told this week that the syllabus for each subject will be slimmed down to make it "more manageable and relevant".
The compulsory core of subjects taken by 13-year-olds will be reduced from seven subjects to just three - English, maths and science.
Despite this, most candidates are still expected to carry on offering French, history, geography and religious education as well.
The changes are based on responses to a questionnaire sent out last term to nearly 1,000 prep and senior schools.
Graham Jones, who is headmaster of Repton School in Derbyshire and chairman of the Independent Schools Examinations Board, said schools had shown little desire for radical change but felt the content of some subjects had ecome "unmanageable". Schools also wanted the exams to place more emphasis on skills and less on the recall of knowledge.
"Leaner syllabuses, however, should not imply academically less challenging papers," he stressed this week.
He also pointed out that reducing the compulsory core of subjects to three would simply regularise existing practice, where senior schools were often happy to grant exemptions from subjects that candidates could not offer. It would make little practical difference, he said.
Common Entrance, which is taken by more than 6,000 13-year-olds every year, is set by the Independent Schools Examinations Board but marked by the senior school to which candidates are applying. There are no plans for central marking but the board will now produce marking schemes to indicate the type of responses that the examiners are looking for.