Teachers are set to call for a ballot on national strikes amid a growing row over school funding in England.
The National Union of Teachers says schools will face “terrible cuts” if the incoming government does not deal with rising financial pressures.
Both Labour and the Conservatives have pledged to protect education budgets.
But agreed rises in pay, pension and national insurance contributions will place extra pressures on school budgets along with rising pupil numbers.
The Institute of Fiscal Studies has estimated that schools could face up to a 10% shortfall on their budgets.
NUT deputy general secretary Kevin Courtney said the consequences for schools would be “dramatic”, with teaching jobs lost and opportunities narrowed.
Speaking as the delegates gathered for the NUT conference in Harrogate, Mr Courtney said: “We have to think there will be redundancies in schools as a result.
“We think it is a very difficult situation for schools in the next year.
“This can’t be right. What we are looking for is the parties to say they will put enough money in.”
The NUT said it intended to hold urgent talks with whichever party or parties form a government after the general election in May before seeking industrial action.
But a motion to be debated by the conference says that “if no progress is made in talks with the new government on the issue of funding” the union should be prepared take strike action.
The timing for the ballot is not decided, but if delegates back the motion due to be held on Sunday, industrial action seems unlikely before the autumn term.
Labour has said it would protect the schools budget, from three- to 19-year-olds in line with inflation, while the Conservative have promised to protect per pupil funding in cash terms but not accounting for inflation.
Liberal Democrats have pledged to protect school, early years and college funding.
If the motion is backed on Sunday, it will require the NUT to work with other unions to “prepare for and ballot for a national campaign of strike and non-strike action” on the “impact of cuts on pay and working conditions”.