Thousands of schools are set to be hit by major disruption after teachers backed a national walkout in a continuing row over pensions.
Members of the National Union of Teachers (NUT) and the Association of Teachers and Lecturers (ATL) have voted overwhelmingly in favour of a strike, according to ballot results.
The action is in protest against the Government's proposed pension changes which the unions say will leave teachers working longer, paying in more and receiving less when they retire.
The Government has said it is committed to working with unions, but that changes need to be made.
A walkout is now set to take place on June 30, affecting millions of children at thousands of schools in England and Wales.
It is the first time in the ATL's 127-year history that the union has voted for a national walkout, with 83% in favour. Turnout for the ballot was 35%.
ATL general secretary Dr Mary Bousted said the result was a "warning shot across the bows" to Government.
"When even the least militant education union and teachers working in private schools vote to strike, the Government would be wrong to ignore it. We didn't want to have to ballot members to strike, but the Government gave us no choice because it is planning to announce a large increase in pension contributions within weeks."
Results from the NUT's ballot show 92% of members were in favour, with 40% of state school members and 27% of private school members voting.
NUT general secretary Christine Blower said she was "very pleased" with the turnout and the result.