Delegates at the National Union of Teachers' conference will voice concerns over Education Secretary David Blunkett's plans to reform secondary schools. A motion from the NUT's leadership will condemn the "damaging, contradictory and untried initiatives".
And it will call on the union to back members in taking action "up to and including strike action, where teaching posts and the conditions of service and employment of teachers are threatened".
Mr Blunkett has marked the new year with a string of speeches that have shifted the Government's agenda to secondary education.
Proposals have included a network of new city academies, set up with voluntary or private-sector backing, an extended school day and a new focus on the transitio from primary to secondary school, where ministers are concerned pupils fall back.
The executive says it rejects any moves to lengthen the school day and condemns plans for tests at the end of the first year of secondary and for new targets for key stage 3 tests taken at 14.
It also condemns Fresh Start scheme which closes and then re-opens schools. The executive blames it for leading to high staff turnover, a collapse of morale and raised alarm over increasing private-sector involvement, which it says is "undermining education authorities and disrupting co-operative work between schools."
The NUT has been fighting for the jobs of teachers in Kings Manor School in Guildford, which has been taken over by private consultants.
The wide-ranging motion also re-affirms the NUT's opposition to selection and condemns the Government's apparent U-turn on grammar schools.