Teachers have backed a ballot for strike action over the Government's proposed pensions changes.
Delegates at the Association of Teachers and Lecturers conference in Liverpool passed a resolution condemning plans which they say would see them work longer, pay more and receive less when they retire.
The union's executive will now consider a ballot, the timing of any action and the form it should take, at a meeting on Tuesday afternoon.
If agreed, a walkout is likely to go ahead this summer. It would be the first time that the Association of Teachers and Lecturers has staged national strike action.
The last time it took a form of industrial action was in 1979, when members were instructed to leave their classrooms on a Wednesday afternoon and hold a staff meeting in a row over pay.
The latest resolution condemns ministers' proposed changes to the teachers' pension scheme, which would see the normal retirement age for teachers rise to 66 and later to 68.
School staff would also be forced to pay increased contributions, ATL says, and the value of pensions could be reduced by 25% on average over the course of a teacher's retirement.
Proposing the resolution, Alice Robinson, a secondary school history teacher and a member of ATL's executive, said: "Teachers will have to work longer - to 66, 67, 68. Can you imagine being a reception teacher and trying to get on and off those little chairs at 68? I think not."
She added: "A ballot for a national strike by the majority of teachers would have a significant political effect. The threat, we believe, would strengthen our hand in any negotiation."
Teachers must let the Government know it has gone too far, Ms Robinson added.