Britain's biggest teaching union has suffered a new setback in its campaign against the workload agreement.
The National Union of Teachers failed to attract enough support for industrial action against the use of cover supervisors.
Only 19 of the union's 51 members at Radclyffe school, Oldham, voted to refuse to cover after the first day of an unforeseen absence in protest at the use of "learning managers" to cover for absent teachers.
With 10 voting "no" the majority in favour was big enough for action under the law, but not according to the NUT's own rule book.
It follows a similar setback in December when the union failed to get the majority it needed in favour of a boycott of national tests.
The Oldham vote was another blow to the NUT's attempt to use the Radclyffe case as a high profile warning to other schools using support staff to take classes unaccompanied, under the workload agreement.
The NUT began its campaign at the school in October, with members refusing to plan, prepare or mark lessons supervised by learning managers. But that action was suspended within a month when the school called its bluff and introduced a system forcing the teachers taking the action to provide the cover themselves.
Doug McAvoy, NUT general secretary, said he was disappointed by the turn-out. "However I can understand why it was low," he said.
"Members did not want to vote 'no' but they did not want to vote for action that could disrupt pupils' education."
The union now wants to negotiate a new package of cover arrangements with the school, subject to consultations with members.
It wants demands on teachers to cover absences to be kept to a minimum and learning managers to cover classes only when external supply teachers are not available.
The package, which forms the basis of guidance being sent to local NUT officials nationally later this month, also states that the managers or cover supervisors should not teach and should not cover lessons for more than three consecutive days of a teacher's absence.
Hardial Hayer, the Radclyffe head, said he would continue talking to staff but that he believed learning managers provided greater consistency than supply teachers. He said he would not compromise standards.
* The public sector union Unison has lodged a claim for a 4 per cent pay rise for school support staff and other local government workers.