Most of the 80,000 part-time teachers in England and Wales are to get a better pay deal that will reward them for work they do outside the classroom.
The package, worth at least an extra pound;40 million, is one of a series of major proposals for the future of teachers' pay and conditions put forward by the rewards and incentives group (RIG), the body made up of the Government and most of the teachers' unions.
The group's weighty influence means its recommendations are likely to be accepted later this year by the School Teachers' Review Body, the independent group which advises the Government on pay and conditions.
But many of RIG's proposals have been criticised by the National Union of Teachers and National Association of Head Teachers, which are outside the "social partnership" with the Government.
RIG has proposed that pay decisions for all teachers should be based on a single system of performance management.
The scheme, which is being developed by the Training and Development Agency for Schools, would introduce standardised performance reviews that would be carried out by teachers' department heads or line managers.
The NUT said that the move would lead to "seismic change" for teachers'
But Chris Keates, general secretary of the NASUWT, insisted the current criteria, which allow all but the most unsatisfactory teachers to progress automatically, would continue. "There is no intention to alter progression on the main scale," she said.
Kerry George, NAHT head of pay and conditions, said the review body's independence was being undermined because it would be forced to fit pay arrangements around the TDA's upcoming performance management system.
RIG also recommends a complete review of the allowances paid to teachers who work with pupils with special needs, warning that some are missing out on the extra pay they deserve. But it said no new incentives were needed to attract more science and maths teachers, calling instead for schools to make better use of those which exist, such as "golden hellos" and higher bursaries.
The NUT has warned that even those incentives create divisions among teachers. The changes, if accepted, will have no immediate effect on teachers' basic pay because a 2.5 per cent salary rise was accepted by the Government last year to cover 2006-2008.
The proposals for part-timers' pay follow research by RIG which found huge variations in how pay is calculated, with authorities using at least nine methods. It showed that some teachers were missing out because no account was taken of the fact that morning sessions they worked were longer than afternoon ones.
A new method recommended by RIG will pay teachers equally for time worked in the morning and afternoons and take account of hours worked outside lesson time and school hours.
Some part-timers are still expected to lose out under the deal, which would be introduced from 2008 and cost up to 0.23 per cent of the pound;19 billion teacher pay bill. But they would be entitled to three-year salary protection deals.
Martin Freedman, head of pay and conditions for the Association of Teachers and Lecturers, a RIG member, said that most part-time teachers would benefit.