Experienced teachers face another obstacle on their way up the pay scale under new criteria proposed by the Government.
To get the pound;1,000 two-yearly increase on the upper scale, teachers will now have to coach or mentor junior colleagues.
The changes come as part of the Government's five-year plan for education, which will also refocus teacher appraisals as teaching and learning reviews that aim to sharpen professional skills.
Under the new pay plans, which Charles Clarke, Education Secretary, wants implemented by September 2006, experienced teachers who have crossed the "threshold" and aim to progress further up the three levels of the upper pay scale will have to show they have made a "substantial and sustained" contribution to their school and have developed their expertise.
And, for the first time, in order to qualify for the biennial upper pay scale increases of more than pound;1,000, they must also "provide regular coaching and mentoring to less expert teachers".
The Government has also backed a proposal made in March by the School Teachers' Review Body to deny underperforming main-scale teachers their annual pay rises, previously seen as automatic. These will now be dependent on written performance reviews from heads.
It also proposes that applications to cross the pay threshold on to the upper pay scale should be assessed independently by "other professionals from other schools".
But unions and other experts believe recent pay changes should be given a chance to bed in before more are introduced. The Rewards and Incentives Group, made up of unions, employers and the Government, issued a clarification of criteria for climbing the upper pay scale just three months ago.
And internal school-based appeals for threshold decisions are to be introduced, following the end of external assessment of applications in September.
Nigel Middleton from Head Support, a consultancy advising heads on the threshold, said using professionals from other schools was likely to be "incredibly bureaucratic". Decisions should be left to heads who knew their staff best, he said.
Steve Sinnott, National Union of Teachers general secretary, said progression through the upper scale should depend on achieving existing targets, not taking on additional responsibilities that ought to attract an extra allowance.
Mary Bousted, general secretary of the Association of Teachers and Lecturers, said she was "very concerned" at the prospect of teachers having to coach colleagues in order to win pay rises. But she saw the new "teaching and learning reviews" to raise teaching standards as part of a quid pro quo with a Government that had been tackling teacher workload.
Chris Keates, acting general secretary of the National Association of Schoolmasters Union of Women Teachers, said: "Why re-invent a system when there is something there already?" But she said would not "go down the line of outright opposition" until she knew the rationale behind the idea.
Ministers are consulting on the plans.
Mr Clarke last week asked the review body to make recommendations on details of the excellent teachers scheme that will replace levels four and five of the upper scale. It was also asked to look at a new framework of management allowances and principles for "safeguarding" existing teacher pay levels.
He also asked the review body whether he should implement the pay rises for secondary maths and science advanced skills teachers proposed in the Smith report on maths and Roberts report on science. The review body has been told to report by January 21.