This year the two headteacher unions sent a joint document and the four unions with largely classroom teacher membership were due to do the same. The funeral of Diana, Princess of Wales, had delayed a meeting by the ATL executive to last Saturday. But after discussion they decided not to sign up because of a clause which said staff should not have to teach classes of more than 30.
Nigel de Gruchy, general secretary of the National Association of Schoolmasters Union of Women Teachers, said the first he knew of the lack of brotherly solidarity was when he opened his newspaper on Monday morning.
Peter Smith, general secretary of the ATL, had accused the other unions of living in cloud cuckoo land by insisting that a maximum class size of 30 should become a condition of employment.
Mr de Gruchy's riposte was: "The decision of the ATL is as perplexing as it is regrettable. Only one year ago the ATL agreed to an identical claim on reducing class sizes to the proposed submission this year.
"Primary teachers in particular will be at a loss to understand the ATL's decision explained in a hurriedly faxed letter on the apparent need for a 'modernisation of policy'. It seems the cuckoo is in the teachers' nest. "
The normally mild Professional Association of Teachers was also quick off the mark, calling the ATL crazy. "Our members are anxious to see some movement on class size as soon as possible," said general secretary John Andrews.
Mr Smith said while his union was committed to class sizes below 30, he thought it pointless to press for a contractual obligation as the Government had made it clear it would not be possible and the review body's view is that it is a matter for school management.
He was not the only teachers' leader to find himself in bad odour this week. Nigel de Gruchy was reported in The Times as saying "an explosion of anger was in the offing" and this was picked up by the TV news. He then warned that teachers may resort to strikes if they continued to be pushed round.
Before matters got out of hand, Mr de Gruchy wrote to Stephen Byers, education school standards minister, saying: "I write to clarify the NASUWT position following a little bit of media hype over the weekend."
But he then went on to tell the minister that if he continued to push teachers' pay below the average he would not raise standards. "May I conclude a hopefully constructive letter by reminding you that MPs are not well placed to lecture others on restraint following the very favourable treatment they gave themselves after the review body report on their own pay," he said.