Independents will be expected to open grounds and facilities to local communities, provide bursaries for poorer students or run outreach programmes. They will be regularly checked by the Charity Commission. Until now the public benefit of charities has been assessed only when they first register with the commission.
The new regime is outlined in Charities and not-for-profits, a modern legal framework, a document launched by David Blunkett, the Home Secretary, this week.
A survey by the Independent Schools Council last month showed that half of fee-paying schools do not share any facilities with state schools. But, nine out of 10 private schools made at least one facility available for outside use to community groups or to businesses.
Alistair Cooke, general secretary of the ISC, said private schools already benefited the public by saving taxpayers money. He said: "Independent schools make a contribution to this country disproportionate to their number. The state is saved some pound;2.3 billion a year as a result of state sector places not taken up by independent pupils."