This ritual must adapt to survive
But are these costly gatherings - the Association of Teachers and Lecturers, the smallest of the big three, estimates its annual bunfight costs Pounds 500,000 - the best way to run a modern union?
Between them, the big three have around 600,000 paid-up members. Yet every year a hard core of 100 or so regular speakers dominates conference debates, the same old faces often saying the same old things. And their decisions can bear little relation to eventual reality.
Yet again, this year the National Union of Teachers' conference voted for national strikes but it has not gone ahead with one since 1969. Delegates from the other two unions are less keen to make threats and the "social partnership" they have signed means their conferences are a chance to mix with senior government officials. It also gives them a chance to hear (and occasionally jeer) education ministers, and every so often the Prime Minister.
But the partnership also means that their leaders take many important decisions behind closed doors. Although their respective conferences still hold them accountable, the real focus of power is shifting. Widespread coverage is guaranteed because they take place when little else is going on. But the number of national media organisations sending representatives is declining.
And there is competition. During the Easter break, teachers gathered for conferences organised by the Maths Association and the Geographical Association. The Specialist Schools Trust's glitzy conference in autumn attracts 2,000 heads.
And the Association of Science Education conference held over Christmas has around 3,000 delegates, dwarfing the 1,100 or so who attend the biggest union gathering held by the NUT.
So it is no surprise that changes are afoot. Future ATL conferences are likely to include seminars with small groups of delegates going off to discuss particular topics before bringing back a resolution for conference to consider. "People who feel intimidated by speaking to the whole conference hall might feel better able to contribute," explained Mary Bousted, ATL general secretary.
This year, the union voted to limit the number of resolutions from an individual branch to five, to encourage a greater variety of speakers.
The National Association of Schoolmasters Union of Women Teachers is encouraging fresh blood with a new Young Activist of the Year award in memory of Eamonn O'Kane, its former general secretary, who died last year.
Meanwhile, an NUT working party set up to look at improving the union's democracy is recommending that local branches encourage more young members to attend conference by subsidising accommodation for their partners. A union survey found none of the respondents aged 30 or less had ever been a conference delegate.
Steve Sinnott, NUT general secretary, has stopped inviting the politicians whose speeches have been the trigger for rowdy scenes in the past. Instead, he wants to hold a separate "state of the nation" event and invite the Education Secretary and the minister for lifelong learning in Wales to speak.
A small step, but it signifies a growing willingness to re-examine the traditional teaching union conference.