Unison, the biggest support staff union with 200,000 members in schools, announced that a large majority of members had backed a strike. A formal ballot is now required, but an initial strike has been pencilled in for Wednesday, March 23, with the threat of more.

The National Union of Teachers was considering joining the action this week, but its executive is split over whether to strike.

Even without the NUT the Unison strike will be devastating for schools.

Support staff strikes in Brighton and Hove over pay led to more than half of schools closing and others sending pupils home.

The changes, proposed for April, a year earlier than for the rest of the public sector, will prevent support staff in England and Wales from retiring on a full pension before 65, raise the minimum retirement age from 50 to 55 and increase contributions.

Unison claim they are another example of low-paid support staff getting a worse deal than teachers.

Teachers’ retirement age does not increase until 2013, with the minimum age changing in 2010, but support staff will be affected this year.

Christina McAnea, Unison’s head of education, said: “Strike action is a last resort and is incredibly difficult to get school staff to take because they are such committed workers. But there is huge strength of feeling about this.”

Schools in 62 local authorities will miss the strike as they will have broken up for Easter. But more protests can be expected to follow.

Left-wing NUT executive members are backing a motion proposing strike action over pensions, to be discussed this week. Dave Harvey, a London member, said: “If we don’t take action on the loss of five years’ pensions then what will we take action on?”

But Jerry Glazier, of the centre-left Broadly Speaking faction, speaking in a personal capacity, said he felt a strike ballot at this stage could be a tactical error because there was no groundswell of support for action. He wanted the NUT to continue to lead the campaign against the changes.