John Maybury, a school rep for the Association of Teachers and Lecturers, admits that his union has effectively negotiated him a pay cut.
As head of music at Brays Grove school, Harlow, Essex, he receives an extra pound;5,688 a year in management allowance payments.
But under a new agreement reached between the Government and most teacher unions, he will qualify only for a teaching and learning responsibility payment worth a maximum of pound;5,500.
To gain a higher responsibility payment of pound;6,500-pound;11,000 he would have to manage a significant number of staff. However, he is the only person in his department.
Helen Binns, the head of the small 500-pupil secondary, fears that a significant minority of her 36 staff will face a pay cut if the deal between the Government and teacher unions to change management allowances goes ahead.
She also says that she may not be able to afford to promote half of those on level two to level three of the upper pay scale, despite a deal which is supposed to provide increases for around 80 per cent of those on level two.
The changes are the product of two agreements reached between the Government, employers and all major teaching unions except the National Union of Teachers.
One deal relies on secondaries finding more than half the cost of promoting teachers to level three from savings in management allowances, with primaries finding just over a sixth.
But Mrs Binns has been able to make only small savings through this year's freeze in allowances. As a result she will be pushed to fund even half of her dozen teachers on level two to level three.
She said: "This is yet another instance of the Government saying it is over to you, so that if things do come a cropper then it is not the Government's fault."
If the School Teachers' Review Body agrees the latest deal, all schools must carry out a full review of their staffing by the end of next year.
Any staff receiving management allowances for administrative duties or recruitment and retention reasons would lose them after three years, under a new system that will make allowance payments only for specific teaching and learning responsibilities. Most Brays Grove staff now receiving allowances - 30 out of 36 teachers - meet the criteria.
The problem for Mrs Binns is how much they will be paid. New responsibility payments will be worth between pound;2,250-pound;5,500 unless staff manage a "significant" number of people, when they will be worth between Pounds 6,500-pound;11,000.
At Brays Grove there are heads of very small departments, with four management allowance points, worth pound;7,833, who will face a substantial pay cut. Several more staff, who do not manage many staff, are on three points worth pound;5,688 and would also lose out.
Mrs Binns is determined to avoid pay cuts but wonders how she will fund rises if she does not save enough from management allowances.
"If it ends up being more than I can afford, then I will go to my governing body. I hope they will support me and if we go over budget then we go over budget."
Mr Maybury said: "I am a very moderate person but I feel this is once again a case of the Government not funding its own plans."
HEADS MUST DECIDE:
* how many staff on level two of the upper pay scale qualify for level three and a rise of pound;1,128.
* how to fund more than half of the cost from savings in management allowances in secondaries and more than a sixth in primaries.
* how their staff should be structured (by the end of next year).
* how much each teacher will receive when management allowances are replaced by payments only available for specific teaching and learning responsibilities.
* whether they can afford any of the proposed "excellent teacher" posts, replacing levels four and five of the upper pay scale, paid a minimum of Pounds 35,000; or advanced skills maths and science teachers on at least Pounds 40,000.