PA -- Head teachers are to begin voting on whether to take strike action in the continuing bitter row over public sector pensions.
The National Association of Head Teachers (NAHT) is sending out ballot papers to thousands of its members, who have until November 9 to cast their vote.
If the action is approved, it will be the first time members have gone on strike in the union's 114-year history
NAHT general secretary Russell Hobby said: "That reasonable heads are pushed to this extreme demonstrates the failure of the Government's approach to negotiation. No valuation, no costings; just rhetoric on gold plated pensions.
"By taking this action we are making a strong call to the Government to avoid the action by negotiating openly and on the basis of a fair valuation.
"We don't want money from other people's pockets - we will cover our risks - but we don't want extra money taken from public servants and put in the pockets of those who caused the crisis in the first place."
The result is due to be announced on November 9, a few weeks before the TUC's day of action in protest at the Government's controversial plans to increase pension contributions for millions of public sector workers.
The NAHT represents 28,500 head teachers, as well as deputy and assistant heads, in schools across Wales, England and Northern Ireland.
Three other teaching unions, the Association of Teachers and Lecturers (ATL), the National Union of Teachers (NUT) and the University and College Union (UCU) took part in a walkout in June over the Government's proposed pension changes.
The unions say the changes will leave them paying in more, working longer and receiving less when they retire.