Teachers at 30 schools in England and Wales are still in dispute over senior staff pay, nine months after new staffing structures were announced.
Five schools have been notified of planned strikes next week by the National Union of Teachers with action at other schools expected to follow.
The dispute is over the replacement of management allowances with teaching and learning responsibility payments, a process which will cost some teachers up to pound;10,500-a-year.
A total of 42 schools acrossEngland and Wales have so far suffered TLR-related strikes this year. The new pay sytem was agreed between the Government and the teacher unions and employers which are part of its social partnership, as a way of ensuring that senior teachers' get paid for duties that will raise standards.
It was also expected to reduce salary bills allowing savings to fund teachers' progression up the upper pay spine. But a TES survey, carried out in February, found nine in ten schools would face increases in their salary bills of up to pound;100,000-a-year.
John Dixon, NUT assistant secretary, said the union was starting fresh disputes in schools where the implications of changes were only just becoming apparent or where school had been late in deciding how to implement TLRs.
All schools were expected to have written new staffing structures by the beginning of this year. Other disputes have been carried over from the last school year.
NUT members plan to strike at Counthill and South Caderton schools in Oldham, at Woodside High in Haringey, north London, Northwood in Hillingdon, west London and Priory sports and technology college in Preston, Lancashire.