A teachers' union which has never taken national strike action before is threatening to stage a series of school walk-outs starting this summer.
The traditionally moderate Association of Teachers and Lecturers overwhelmingly backed a ballot on strike action over a government threat to teachers' pensions.
The union, which is strong in state grammar schools and independent schools, will take national strike action in June if its members back the move in a ballot. More strikes will follow in the autumn if ministers do not back down over their plans. As a result of their review, teachers will be asked to contribute an extra, on average, £100 a month to their pensions. Union financial experts say the value of the pension will fall by around £100 a month. In addition, the retirement age will be raised to 68.
Richard Ainsworth, an independent school teacher from Cheshire, said: "This is a massive insult."
The ATL is almost certain to be joined in any strikes by the National Union of Teachers, which will debate a similar motion at its conference to be held over the Easter weekend.