The assumption that teachers will receive automatic pay rises as they stay in the profession has been thrown into serious doubt by education secretary Michael Gove this week.
Mr Gove signalled his intention to introduce performance-related pay for teachers and called for investigation into whether the existing pay scales are a "barrier" to reform.
The move came in a remit handed from the education secretary to the School Teachers' Review Body (STRB) - the organisation he is obliged to consult on teachers' pay and conditions - in which he asked how pay scales "should be reformed to more effectively link pay and performance".
The highly contentious suggestion comes as teachers are already partway through a two-year pay freeze and facing having to pay significantly higher contributions to their pensions.
The proposed reforms raise the prospect of teachers being barred from pay rises unless they reach goals set by their managers or seek promotion to posts with more responsibility.
Martin Freedman, head of pay and conditions at the ATL union, said the plans were a "huge step backwards" for the profession and raised the fear that financial pressure on schools could stop heads offering pay rises.
"A teacher could be missing out, not because they are not performing well, but because the school is short of money," Mr Freedman said. "It's like in the 1980s, where you moved up the pay scale only if you were in with the head. Once you start taking away objectivity from the system, how can we be sure it will operate fairly?"
Andrew Morris, head of pay at the NUT, also heavily criticised the idea that automatic progression could be scrapped and replaced with performance-related rises.
"We don't feel there is a case for performance-based pay in teaching," Mr Morris said. "You can't really measure how well a teacher is contributing to the education of a class; the circumstances of individual students have to be taken into account."
At present, teachers' pay increases automatically as they progress up the main pay scale, unless their head makes a case why it should not. After six years' experience, teachers can pass through the "threshold" on to the upper scale if their teaching is of a high enough standard, with the vast majority able to make that step.
Mr Gove's letter follows a warning by the new Ofsted chief inspector Sir Michael Wilshaw that heads could come under pressure from inspectors to justify any pay rises they give to staff.
Sir Michael said that it was "quite legitimate" for inspectors to ask heads "How many of your staff have moved up the main (pay) scale" or "How many have gone through the (upper pay) threshold?"
The proposal also further undermines the status of national deals on pay and conditions, with academies and free schools already exempt from the agreements.
Russell Hobby, general secretary of heads' union the NAHT, said he was unsure whether "a crude bonus structure" of performance-related pay would work in schools, although he added that it could allow talented young teachers to rise more quickly up the pay scale.
But the move was welcomed by James Groves, head of the education unit at right-leaning thinktank Policy Exchange. "It's definitely a question that needs to be asked. I'm not sure we can get more teachers to come forward to join the profession unless we shake the system up a bit. Some younger teachers I know would be in favour of this," he said.
The STRB has also been asked to look at the pros and cons of introducing regional pay, and for advice on how to "make pay more market-facing for teachers". Businesses have claimed that national pay deals serve to disadvantage firms in less prosperous regions that cannot afford to keep pace. The unions have argued that regionalising pay could lead to a recruitment crisis in less well-paid areas.
"If you get offered pound;5,000 more in place X than place Y, there is no competition," Mr Morris said. "It's got to be a pay-cutting agenda."
In Mr Gove's letter to the STRB, members are reminded that any changes "should not lead to any increase in paybill in the long or short term".
The body has been asked to report back to the education secretary by 28 September.
Main pay scale
Annual pay: England and Wales (excluding London)
Scale point 1
Scale point 2
Scale point 3
Scale point 4
Scale point 5
Scale point 6
Upper pay scale
Scale point U1
Scale point U2
Scale point U3.
Original headline: Automatic pay rises for staying in the classroom at risk