Private schools could abandon the "fashionable" national curriculum for a return to 1950s-style education.
Headteachers at many of the country's prep schools argue five to 14-year-olds should be taught key historical dates, spelling and times-tables - rather than government-ordered classes on obesity, parenting and citizenship.
The proposal risks widening the academic divide between state and private education and comes as the government launches a new initiative to involve private schools in their wider communities.
Speaking at the Independent Girls' Schools Association conference in Leeds, Michael Spinney, chairman of the Independent Association of Prep Schools (IAPS), said the national curriculum is "overwhelmed" by a "social agenda".
"That social agenda is not something that we want to get sucked into," he told delegates. He urged other independent school associations to join in a debate about the future direction of the curriculum.
Private schools are under no obligation to follow the national curriculum but the proposal, still in the early stages, would see headteachers take a firmer break from the centrally-set curriculum.
Lessons would have to remain broadly similar in key respects, however, to ensure privately educated pupils could sit GCSEs.
Mr Spinney said yesterday: "Increasingly, we are living in an era where teaching and learning are sacrificed in favour of fashionable causes, often with disastrous effects upon standards of learning. The time has come to set up an independent schools committee to analyse the national curriculum.
"The government is increasingly putting a social agenda into the equation. It has an issue about multicultural society and subjects such as slavery. What we're interested in is knowledge, rigour and fundamental skills."
The government insists it has already reformed the curriculum to make it more flexible, giving teachers more time to concentrate on the so-called "basics".
A spokesman for the Department for Children, Schools and Families said: "A curriculum which reflects the world in which we live helps to engage children in learning and give them the knowledge they need to succeed, but it does not follow that teaching and learning is less academically rigorous.
"Nobody with any sense could believe schools could teach the second world war, a statutory requirement, without covering Winston Churchill and Hitler."
Yesterday, ministers announced an initiative designed to forge closer links between the state and private sectors.
Schools minister Lord Adonis confirmed a £4 million fund to help private schools tutor "gifted and talented pupils" in the state system.
The scheme will fund master classes in core subjects and coach state school pupils applying for Oxford and Cambridge.
Lord Adonis insisted the move was "in no way a commentary on the state sector".