Independent schools have agreed a code of conduct to avoid any future allegations of fee-fixing.
The Office of Fair Trading is investigating claims that several leading private schools, including Winchester and Eton, broke the law by collaborating over fee increases. That investigation has prompted the Independent Schools Council, which represents most private schools in the UK, to draw up a code of conduct that bans even telephone conversations about fees between schools.
The Office of Fair Trading has approved the code, although its investigation is continuing.
Under the agreement, the 1,300 member schools have been told: "There must be no direct or indirect disclosure of commercially sensitive information about (your) school to other schools. If, during the course of a telephone conversation with another school, any commercially sensitive information is volunteered or requested by that school, the conversation must be discontinued immediately."
The 1998 Competition Act made it illegal for private schools and other bodies to operate as a cartel. Alistair Cooke, general secretary of the council, said: "It is important to stress the absolute commitment that member schools have to ensuring that they proceed in accordance with the law." He said there had been no discussion with officials over the investigation, which is expected to last months.
The code of conduct is similar to the one being adopted by St Paul's Boys' School in London, which was floated as a blueprint for other schools when it was disclosed by The Independent last month. That code also warned staff to avoid discussing fees on the telephone with rival schools.