Until now the findings of HMI, who visit a failing school six months after its original inspection, have remained private, but the Office for Standards in Education believes it now has a legal duty to release the information if requested.
Heads have warned ministers that six months is not enough time for a school to be turned around and that a fresh bout of damaging headlines could put its future in jeopardy.
The Act, which came into force on January 1, requires public bodies, including schools, colleges, universities, local authorities, quangos and government departments, to disclose information requested by the public.
Information can be withheld only where a specific exemption, such as public interest, applies.
Schools will have to respond to requests within 20 working days and there is a duty on them to provide advice and assistance to those requesting information.
Heads said schools would be forced to change the way they keep records in order to protect information they do not wish to make public. But they will have no control over information held by other bodies, including Ofsted's judgements on schools in special measures.
David Hart, general secretary of the National Association of Head Teachers, said: "I do not see that there is anything to be gained from putting a failing school through the mill again so quickly and publicly when it should be given time to put its house in order."
John Dunford, general secretary of the Secondary Heads Association, called on the Government to look again at the impact the Act will have on schools.
He said inspectors may water down their interim findings on failing schools for public consumption.