David Blunkett, the Education and Employment Secretary, will be asked to grant three birthday wishes next week when he attends the centenary celebrations of the National Association of Head Teachers.

The union finds it propitious that on its 100th birthday he will be making his first keynote speech to teachers since taking up his new office. Liz Paver, who takes over as the union’s president on Tuesday, has her wish-list ready: less contact time for primary teachers, a pruning of the curriculum, and smaller class sizes.

She believes the union, which has weathered two world wars and seen many Education Acts come and go, has seen the most revolutionary changes to the headteacher’s job in the last 10 years, with the introduction of local management, increased role of governors and national curriculum.

The 1905 Handbook of Suggestions for Teachers, which said, “The Head Teacher was to be captain of his ship, and was free to adopt whatever methods he considered best for the well-being of his school”, has become a quaint curiosity.

David Hart, who also celebrates his 20th year as general secretary, says the union’s founding members would be proud to see the emergence of the NAHT as the biggest association for heads and deputies in Europe and the second biggest in the world.

According to a book published half a century ago to mark the union’s 50th year, drawing on the experiences of its former presidents, its beginnings were somewhat shaky.

According to F V Hawkey (the president from 1942 to 1943), the newly-formed association had its trials. Some heads thought becoming a part of the horny-handed brotherhood of toil was not in keeping with their station.

He said: “It was not ‘quite the thing’ for the black-coated worker to indulge in the radical method of procedure associated with trade unionism, and the professions were expected to hold themselves aloof from anything in the nature of agitation and concerted action. Undeterred by forebodings of the loss of social status and unperturbed by warnings of all kinds of dire consequences, the stalwarts persevered and the association grew in size and influence.”

Since then NAHT has lost any inhibition over fomenting agitation, and members famously booed John Patten, then the Education Secretary, to much indignation from the popular press.

But some things remain the same. David Hart said: “If any of our founding members were to appear on the scene in Scarborough next week, they would not be unfamiliar with the issues important in 1997.”

Prominent on the 1925 agenda of the association was the need to rebuild unsuitable school buildings. The problem of class size, however, was of an altogether different order in earlier days. One teacher recalls that in 1900 classes of 80 or more were not unusual and one mistress who had a class of 99 and said she regretted it was not 100 because then she could have “made a song about it”.

The history of the union also reveals the waxing and waning of educational ideas, many of which have now come full circle. Past presidents rejoiced in being freed from the rote of the Three Rs. “The embryo of totalitarianism in education was withering and passing away before reaching a stage of development which would have stultified all further progress,” wrote F V Hawkey.

This freedom allowed primary school teachers’, unburdened by a national curriculum to become visionaries. “In the infant school we do not want level pitches upon which to play football in the orthodox way,” said Dorothy J Neale, speaking in the late 1940s. “We want an adventurous environment where we can try out our new-grown strengths . . . We want hills to roll down and to climb, cosy and grassy dells to sit in, mounds upon which to climb and shout . . . Yes - we need trees.”

The NAHT conference has taken a number of forms, but the innovation of the one-minute mike spot (to be extended to two minutes) has been the most popular. This allows delegates to stray off the prepared platform speech and always has that element of danger. One of the most memorable was the headteacher who got up to lambast his colleagues for spending school funds on lavish furniture for their offices.

The conference last year said goodbye to its Saunders and Grey double act, the headteachers from Stoke on Trent whose attempts to remove the stuffiness from proceedings made them popular performers.

“Education is boring. Not even Tony Blair could make it interesting,” said Martin Saunders. “Derek Gray and I just tried to make it look as if headteachers had a sense of humour, while making important points.”

He paid tribute, as did many of his colleagues, to the general secretary for his part in the NAHT’s success. “Without any shadow of a doubt, David Hart is the best general secretary of all the trade unions and we have been very fortunate to have him,” he said.

The union’s main rival is the Secondary Heads Association. David Hart says he would like the 8,700 SHA members and 32,000 NAHT members to come together under an umbrella association. Liz Paver says she will try to forge new links in her presidential year. While they do work together on policy documents, and there is fair amount of double membership, both sides admit there are still major obstacles to a merger.

The immediate prospect for the NAHT is to highlight to Mr Blunkett, its special birthday guest, its present concerns: heads’ pay, the professional development of school managers, problems with the inspection service, the unpopularity of collective worship and target setting.

Mr Hart said: “As we celebrate our 100th birthday, it is appropriate that we have a new Government. I do not look upon its new programme with rose-tinted glasses, but I look forward to a meaningful relationship and a meaningful partnership.”