Staff in small schools who take on extra duties are not getting more pay because heads do not have enough cash to fund increased salaries, the NASUWT conference will hear next week.
Limited budgets cannot support the number - especially in primaries - who have to take on extra-curricular and pastoral responsibilities, say Chris Brown and Sue Vowles, of the teacher union's north-east Essex branch. They are calling for a review of the funding system to prevent teachers losing out.
They believe many heads are also using budgetary constraints to "pressurise" teachers into taking on subject co-ordinator roles without appropriate pay allowances.
Employers are in breach of contract if they do not give teachers statutory entitlements. Mr Brown and Ms Vowles want the union to take more action against schools that fail to pay properly.
The School Teachers' Pay and Conditions Document 2008 says teachers cannot "be expected to take on the responsibility of, and accountability for, a subject area or to manage other teachers without appropriate additional payment".
NASUWT members will vote on whether the union should work with social partners to find small primaries that are managing to pay staff with extra responsibilities or leadership positions properly.
Mr Brown and Ms Vowles want the union to work with the Training and Development Agency for Schools to produce a toolkit to help small schools to manage salaries.
They also want the agency to examine school budgets, especially in cases where heads claim they do not have enough money to increase pay for extra duties.
If budgets are insufficient, they want the funding system revised.
As The TES has reported, the NUT wants a salary increase of Pounds 3,000 or 10 per cent for all teachers. It also wants a merger of the main and upper pay scales, the establishment of an inner-London allowance of Pounds 7,500, an outer-London allowance of Pounds 5,000, and fringe allowances of Pounds 3,800.