Quotas and positive discrimination to ensure women get more of the top jobs in schools have been ruled out by the ATL, despite delegates being told of a typical male primary head sitting in the staffroom "like a sultan in a harem".
Government statistics show that out of 32,000 male primary teachers, 48 per cent are heads or deputies but only 16 per cent of 149,000 female teachers are in similar posts.
Out of 93,000 male secondary teachers, 9 per cent are heads or deputies compared with 4 per cent of 96,000 female teachers.
Hilary Pollard, of Kirklees, who chairs the ATL's equal opportunities committee, said: "I don't believe that so few women are incapable of being heads and deputies. I am absolutely certain that prejudice is responsible for that tremendous disparity in the figures."
Maureen Williams, from Doncaster, said: "In most primary schools you will find that the person at the top is the man. If you call at break or lunchtime, you will find him sitting in the staffroom like a sultan in his harem."
The debate over a motion calling on both national and local government to seek to promote a more equitable distribution of headships was one of the most heated during the three-day conference.
But it was won in the end by speakers who argued that it would lead to unfairness. Stephen Woodley, of Kent, said: "The motion seems to encourage central and local government to practise positive discrimination, and positive discrimination scars. We should not be encouraging the association to support a policy that avowedly seeks to discriminate against men."
Stuart Herdson, from Bradford, insisted promotion had to be awarded on an equal basis: "It would be a really bad thing to see a quota of headmistresses. "
The motion, put forward by the Doncaster branch of the ATL, was backed by the Women in Education Network, which said women needed better access to continuing professional development and preparation to apply for headships. It said childcare and cr ches needed to be provided, rather than squandering resources on bureaucratic schemes such as nursery vouchers.
In Wales, it said, 79 per cent of primary school teachers were female, yet only 44 per cent of headteachers were women.
John Parkinson, of Doncaster, proposed the motion and told delegates: "We are not asking for quotas. We are asking for equal opportunities. I am not asking for positive discrimination. I am asking for justice for our women members. "