A vote carried out with head teachers to decide if a ballot should be staged as to whether teachers should strike over changes to their pensions was unanimous in favour of the ballot.
Of the 350 delegates at the National Association of Head Teachers annual conference, all but 1 head teacher voted in favour of the ballot in Brighton.
With this union having never gone on strike before, thousands of schools in the country could be faced with a unique prospect of having no teachers for a day.
With the government yet to announce final plans for changes to teachers pensions, unions are currently guessing at the changes, something the government is urging them not to do until the actual announcement in the autumn.
Lord Huttons review called for the current final salary scheme to be replaced as it is not affordable in the long run for the government, and called for a fairer average salary scheme, one that is still far more generous than most private pensions.
Changes to the scheme are expected to cost head teachers around £100,000 from their pension and the extended retirement age will mean they have to work longer for their money.
The head teachers are planning to run their ballot in the autumn, and would most likely strike soon after, in the autumn term.