School leaders are set to join teachers in taking industrial action over controversial pension reforms.
Heads' union the NAHT is today expected to announce that it will hold its own ballot after it was revealed this week that the NUT and ATL unions had voted overwhelmingly in favour of going on strike.
The NAHT national executive was due to discuss what industrial action to take, with a strike being one of the options under consideration.
Speaking to TES Cymru before the meeting, NAHT general secretary Russell Hobby said: "Our members didn't need any more of a message about the other unions' support for strike action - the way they feel is already strong - but it will help harden the views of some.
"We will have to put on our managers' hats while we deal with this strike, but we will be planning our own ballot timetable, depending on what our national executive decides."
The "vast majority" of schools in Wales will be forced to close on June 30 because of the NUT and ATL action.
ATL members are to take to the picket line for the first time in the moderate union's 127-year history, after 83 per cent of those who voted backed the national strike, on a turnout of 35 per cent.
The NUT will also be striking, with 92 per cent of teachers in favour, on a turnout of 40 per cent.
The unions said the action was forced on them by planned changes to the Teachers' Pension Scheme by the Westminster government.
Dr Philip Dixon, director of ATL Cymru said: "What happens next is up to the Westminster government. If it negotiates in good faith then disruption can be averted.
"But if it continues to push ahead with these plans we have no choice. We will defend teachers' pensions and there will be a strike. The vast majority of teachers in Wales are prepared to strike to defend their rights."
David Evans, secretary of NUT Cymru, said the unions had the support of the general public and the headteacher unions.
"We have had one or two calls from people concerned about it but nothing like the sort of numbers who called when we last went on strike three years ago," he said.
The Westminster Government has proposed increasing pension contributions by 50 per cent, which would cost teachers an extra #163;1,145 per year on average. The retirement age would also gradually rise to 68.
Although powers over teachers' pay and conditions are not devolved to Wales, the unions said they hoped the Welsh Government could put pressure on Westminster to resolve the dispute.
A Welsh Government spokesman said: "In the event of industrial action it is schools' and local authorities' responsibility to minimise the impact on pupils' learning."