The two largest teachers' unions have put down motions at the annual gathering in Blackpool against ministers' moves to create a "post-comprehensive" structure.
This summer Education Secretary Estelle Morris set out plans for a five-tier "ladder" of secondary schools, with failing schools at the bottom and advanced specialist secondaries at the top.
In its motion, the National Association of Schoolmasters Union of Women Teachers will argue that the Government has failed to address inequality in the current structure. And its enthusiasm for specialisation and selection risk recreating the elitism inherent in the grammar-school system.
The National Union of Teachers' motion argues that ministers should concentrate on improving education for all pupils.
Both unions are supporting a motion from Unison, the public-sector union, which would see the TUC opposing, for the first time, private finance initiative schemes for the public services.
Ms Morris will address the conference on Wednesday on the part that unions can play in improving skills in the workplace to raise Britain's competitiveness.
Nigel de Gruchy, former NASUWT general secretary, is set to be elected president of the TUC at the congress.
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