Huge changes to secondary schools and the way they are led have been mirrored by the SHA, which is enjoying more members, diversity and influence than ever before as it celebrates its silver jubilee this weekend.

When formed in 1978 the organisation was dominated by grammar school heads, had no premises to call its own - it shared with the Assistant Masters’

Association. Annual conferences were intimate affairs, held in Oxbridge colleges.

In the early days it was, according to former general secretary John Sutton, “almost a kitchen table organisation” with a ratio of male to female members of three to one “at best”. Two decades later, Judith Mullen had become SHA’s fifth female president. But even in 1994 when she first became an active member, she felt like she was joining an “old boys’

club”.

Today she is pleased to note that the council is roughly half men and half women and has seen a “definite change in atmosphere”.

The SHA’s origins go all the way back to the late 19th century when its forebears, the Headmasters Association and the Association of Headmistresses were founded, in 1890 and 1874 respectively.

Early concerns included whether the 1902 Education Act, extending state support for education, would damage the status and prestige of the older established schools they represented. Other issues have a more familiar ring to them, with teacher shortages proving a major worry during the 1950s.

Although the associations worked together for many years they did not manage to agree on everything. While the HMA supported the general thrust of the 1944 education bill it was determined to defend grammar schools.

A conference resolution read: “Whatever the eventual future, for years to come we shall be predominantly an association for heads of secondary schools of the old style.”

The AHM took a very different stance and in 1943 president, Agnes Catnach, said: “We can only hope that our colleagues in whatever new girls’

secondary schools materialise will be ready to explore with us, ways of working together so that the new and the old may be built up together into the kind of spiritual unity... from which we of the older system have gained so much.”

John Dorrell, leader of the HMA, by far the biggest of the two associations, managed their merger in 1978 and became the SHA’s first general secretary.

By the end of the year he had been succeeded by Donald Frith, who was followed by Peter Snape in 1983 and then by Mr Sutton, who led for 10 years from 1988.

Annual conference has always been a highlight and memorable moments over the years included Conservative education secretary John Patten raising a few eyebrows when he presented SHA with a ruler to measure its success with. The late Robert Maxwell, owner of Mirror Group Newspapers, got a severe dressing down from an irate female head in 1987 after unwisely including a swear word in his speech.

Membership broadened significantly with the admission of deputy heads in 1983, and assistant heads in the mid-1990s.

And for the future? Speculation about a possible merger with the National Association of Head Teachers, rejected eight years ago, continues. But John Dunford, the SHA’s fifth general secretary, refuses to be drawn on this, saying: “I want the SHA to become sufficiently influential so that no minister thinks of making any change to secondary education without consulting us first.”