The strikes, by National Union of Teachers members, are planned for July 11 at Gowerton and July 12 at Cefn Hengoed. Members are in dispute over the introduction of new “teaching and learning responsibility” payments (TLRs), which replaced the old management allowances from January.

As TES Cymru went to press, crisis meetings were taking place at the two schools, involving the union, local education authority representatives and school governors. NUT members have already approved strike action in ballots held at each school.

David Evans, NUT Cymru secretary, said some teachers who currently receive a management allowance had not been offered new TLR posts, with some standing to lose up to pound;5,600 a year.

Although the strike at Gowerton had not been called off (as of Thursday), governors there had promised to consider an alternative staffing structure proposed by the union, he said.

Mr Evans added: “We will do everything we can to avoid this action and I hope that progress can be made this week.”

Wayne Newton, head of Cefn Hengoed, said: “I am hopeful a strike will be averted. Although we have some staff who are losing money, there are far more people gaining. New posts have been created which are ring-fenced for people already here.”

A spokesperson for Swansea LEA said: “We are disappointed at the strike threat as both schools have complied with legal requirements and have followed national and local guidance and advice.”

Gowerton headteacher Paul Green said he and the school’s governors were “deeply saddened by this action, which we regret”.