Anyone walking near Westminster a few Saturdays ago might have been surprised to see a collection of figures in Victorian garb wandering the streets. They were members of the National Union of Teachers, trying to persuade the public that as the world prepared to enter a new century, the Government was attempting to push their profession back into the previous one by reintroducing payment by results. In other words, that 100 years of teachers’ union gains were under threat.

Whatever the rights and wrongs of the argument, great gains have been made since the 19th-century system of paying schools according to their pupils’ performance died out. The history of education in the 1900s has been in part the history of the unions.

There were already six teaching unions in England by 1900: the NUT, founded in 1870 and by far the largest, the National Association of Head Teachers and the “joint four” - associations representing secondary headmasters and mistresses and assistant masters and mistresses.

From the start, their battles have been as much about professionalism and equal rights as about pay. The NUT’s biggest early success was the creation of national salary scales, under the Burnham committee, formed in 1919. The union, which had gone on strike repeatedly over pay, won negotiating rights that would last almost 70 years.

But 1919 also marked the start of what historian Brian Simon would call “the dark era between the wars”, when education came under attack from the twin forces of conservatism and economic crisis.

Some people argued that teachers did not deserve Burnham’s pay rises. The Daily Mail claimed in 1924 they were “distinctly overpaid” - teaching was only a “moderate accomplishment”. Teachers suffered pay cuts of 5 per cent in 1921 - there were strikes around the country - and 10 per cent in 1931.

The unions also fought for women’s rights. The NUT adopted equal pay as policy in 1919 but could not prevent the breakaway of the National Union for Women Teachers in anger at the slow pace of change.

The National Association of Schoolmasters also split away in protest. “The application of equal pay I is unjust to the schoolmasters, the boy in the school, the taxpayer and the ratepayer,” it said.

In 1923, women teachers were paid pound;254 a year, compared to male colleagues on pound;310. Worse, they were forced to resign if they married, as it was considered impossible to keep a home and teach. It would be 1944 before the NUT won an end to the marriage ban, and 1961 before equal pay scales were introduced.

The 1944 Education Act introduced the NUT’s long-sought goal of universal education - a milestone for the union, according to former general secretary Fred Jarvis. A second milestone was the achievement of a graduate-entry profession. A third was the Houghton pay commission in the 1970s, when pay returned to dominate the unions’ agenda.

Houghton delivered a 25 per cent pay rise. But high inflation quickly eroded it, and by 1979 the NUT argued that teachers had fallen 30 per cent behind comparable professions. Attempts to close the gap led in 1984 to industrial action by the NUT and the National Association of SchoolmastersUnion of Women Teachers. (The UWT was no relation of the long-defunct NUWT).

Three years of action included the first national strikes for decades. At their conclusion, Margaret Thatcher’s government, in no mood to accommodate militant unions, peremptorily scrapped the Burnham pay scales outright.

If the 1980s marked the modern high-water mark of teachers’ militancy - particularly in the NUT - then the influence of the Left has waned, despite the decade of unprecedented change that has followed.

The NUT, though still the largest union, no longer dominates as it did. The NASUWT’s membership has grown hugely, and the Association of Teachers and Lecturers - like the Secondary Heads’ Association, a product of the old “joint four” - is a significant voice. Some think they would be more effective if they were a single body.

The unions now see themselves as moderate forces tempering the excess of change, or helping to make it work. Occasionally they have been pushed too far - as with the introduction of national curriculum tests in the early 1990s or the workload campaigns of last year. But often they have been portrayed as prophets of doom with each reform.

If the unions were seen 100 years ago as dangerous forces for progress, now they seem close to being tarred unfairly as forces of conservatism, to use the phrase Tony Blair minted for the millennium. That irony is worth dressing up for in Victorian costume and wandering down Whitehall.

* WHAT THEY SAID ABOUT THE UNIONS

“They (the NUT) have always fearlessly attacked all absurdities of our educational system, have never cringed before officialdom, have stood for progress - never for apathy or reaction - have constantly and consistently used their powerful influence for the good of the child as well as of the teacher.”

Sir George Kekewich, Secretary of the Board of Education, 1900-1903 “Teachers make bad trade unionists. It is as if this was for them one role too many. Most teachers join a union not to stand up for their rights, but to give them legal protection. Meetings are badly attended and most teachers remain illiterate about education politics. This illiteracy is for some a source of pride. They betray their fellow members without guilt and with a perverse sense of virtue.”

RT Spooner, head of a Leedscomprehensive school, 1981 “In all my many dealings with the NUT ... I never once heard mention of education or children. The union’s prime objective appeared to be to secure ever decreasing responsibilities and hours of work for its members, and it seemed the ideal NUT world would be one where teachers and children never entered a school at all - and the executive of the NUT would be in a permanent conference session at a comfortable seaside hotel.”

Bernard Donoughue, director of the No 10 Policy Unit during the Callaghan government.