Local authorities were today accused by a teaching union of attempting to "penalise" teachers stranded abroad because of the travel chaos caused by the Icelandic volcano.
The NASUWT said there had been a "steady stream" of advice from local authorities apparently focused on ways of making life "difficult" for teachers who have been unable to make it back for the start of term.
Schools have told to ask for written documentation showing a flight has been cancelled by Birmingham City Council.
There is "no expectation" that a teacher who has failed to inform a school of their delayed return should be paid, the council added.
It also suggested that schools might discuss with teachers making up for lost time through schemes such as summer schools and one-to-one tuition programmes to offset the cost of absences.
Chris Keates, NASUWT general secretary, said: "Employers are clearly spending hours of time producing lists of ways to ensure that teachers, who have been victims of circumstances beyond their control, are penalised in one way or another.
"It is times like this when teachers have the opportunity to see whether the dedication and commitment they give day in day out and year in year out is valued by their employer.
"Sadly, the conclusion in all too many cases is that it is not. Many teachers do not have the good employers they deserve."
Birmingham City Council insisted it would not be deducting pay from staff.
A spokesman said: "The dedication and commitment of teachers and all school staff is highly valued in this authority.
"The guidance issued to schools was discussed in a meeting with the trade unions during which their suggestions were taken on board and incorporated.
"As circumstances develop the information will be updated and adapted. But it is important to stress that the local authority itself will not be deducting pay from staff."
The NASUWT said it also had concerns about the approach advised by Kirklees, Sandwell and Dudley councils.
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