The Government is urging teachers not to back strike action, warning it will only achieve "disruption to children's learning".
The National Union of Teachers (NUT) has announced it will prepare for a ballot of its 255,000 members on a series of possible strikes in England and Wales after a one-day strike planned for next month.
The NUT conference in Manchester demanded that ministers give them a 10% pay rise - or £3,000 for every teacher this September, whichever is the greater.
The proposed April 24 strike would hit thousands of schools in the run-up to millions of pupils taking tests and exams.
But a spokesman for the Department for Children, Schools and Families criticised the vote.
He said: "Strike action can only achieve one thing - disruption to children's learning."
"The 2.45% pay award for teachers was recommended to us by an independent pay review body."
It is "above the current consumer price index inflation rate and the Government's inflation target".
"Everybody understands, including teachers, that we need to have a firm control of public sector pay," the spokesman said.
But NUT general secretary Steve Sinnott insisted that teenagers' exam preparation would not be affected.
