The last attempt to merge any of the teacher unions ended in disarray in 1993 when the NASUWT conference decisively rejected the idea. But a new body, Professional Unity 2000, launched with the open but unofficial support of senior members of the "big three", is now on the march. The NUT, whose executive is the most enthusiastically in favour of merger, is to ballot its members again on the issue.
But the omens do not look good. Nigel de Gruchy, of the NASUWT, is still openly dismissive. The new moves will be still-born, he says, and in any case there is no particular advantage in unity.
The profession is so large that a single union would soon dissolve into groups and factions. Even when the existing unions have made joint approaches to government over recent years, he argues, they have been ignored. What he wants to see is an end to the "unrelenting hostility" there has been from recent secretaries of state.
John Andrews, of the anti-strike PAT, is also very aware that the different traditions of the existing associations make combination difficult. Getting three or four organisations to speak together on specific issues might be just as effective as mergers, he thinks.
The NUT is most committed to unity and supports the aims of Unity 2000. "We would go for it and not expect to take our baggage with us," says general secretary Doug McAvoy. Mergers, he thinks, are inevitable in the end but may take a long time coming.
Peter Smith, of the ATL is not unsympathetic in principle, but does not rate the chances highly in present circumstances given the difficulties of presenting a joint case on specific issues. Perversely, he thinks, on the rare occasions when the existing organisations do get their act together on an issue it can be very effective.
The most optimistic prospect for unity lies with the heads and deputies. Both the NAHT and SHA are in favour of merger in principle. The sticking point is SHA's insistence that there should be some form of separate voice for heads of secondary schools.
David Hart, of the NAHT, is anxious to revive talks with SHA, not least because Labour education spokesman David Blunkett is on record as saying that a single association for headteachers would constitute the most formidable lobby in education.