Government delays mean that a long-awaited report, which could lead to ancient colleges being stripped of millions of pounds of benefits, may not now be published until the autumn.
Prime Minister Tony Blair told the performance and innovation unit to review charity law in July last year.
The unit now says it hopes to publish before MPs leave Parliament for the summer, but admits that its report could be pushed back to the autumn.
Insiders believe that schools will not lose their charitable status, although they will be told to do more for the community. Mike Sant of the Independent Schools Bursars' Association said: "We are going to have to do a lot more to make it clear that we are not taking advantage of the benefits of charitable status."
Others believe that a closely defined test of public benefit will be laid down and schools will have to meet it.
But John Shuffrey, a partner at accountant Saffery Champness and an expert on independent schools, said: "Schools have been talking about letting local authorities and schools use their facilities, and about the scholarships and bursaries they provide.
"For a well-endowed school in a city centre, it may be easy to find local schools to use their facilities and to provide bursaries. But what about a not very well-endowed rural school?"