The NASUWT said that from the start of next term its members will no longer cover for absent teachers – and it has warned it will consider ‘a rolling programme of strikes’.
The NASUWT and NEU have each held one day of strike action during the dispute.
In a statement issued on Monday, Chris Keates, NASUWT general secretary, said: ‘Our members are deeply angry and frustrated by the intransigence of the SEB to date.
‘In the absence of progress towards a resolution of the pay dispute then they have no choice but to step up industrial action.
‘A meeting is scheduled to take place with the SEB negotiators today. The NASUWT will engage constructively in that meeting and if good progress can be made then there will be no need for an escalation of industrial action next term.
‘However, if the SEB remains intransigent and does not engage positively then further action cannot be avoided and the Union’s National Action Committee will have no choice but to proceed with the no cover ban and to consider further action including considering a rolling programme of strikes.’