Teaching assistants are refusing to cover lessons to give teachers their half-day a week for marking and preparation, unless they receive better pay.
In Middlesbrough, 12 teaching assistants at Berwick Hills primary have signed a letter to the head saying that they will not provide lesson cover until wages reflect the extra responsibilities. Other assistants will be urged to join the action at a public meeting in the city next week.
A teaching assistant at a Hampshire school has told The TES that she declined to stand in for teachers after being promised just 15p extra to take a class.
This week Unison, the union which represents teaching assistants, said schools will be forced to send children home, as it threatened more industrial action in local authorities proposing to cut its members' pay.
Christina McAnea, Unison's head of education, said it was the single status agreement, aimed at standardising pay and conditions for local government staff, rather than the workforce deal that was causing problems.
The union is to ballot 1,000 Cheshire teaching assistants on action after the county council proposed a pay deal which Unison says will leave its members pound;2,000 a year worse off.
Ms McAnea said action was predicted in up to six other authorities including Middlesbrough, Gateshead and Redcar and Cleveland.
Unison is talking to Ruth Kelly, the Education Secretary, about a national pay structure for support staff and was due to lodge a national claim with employers by the end of next week.
Assistants are being seen as vital to implementation of the workload deal and more than 14,000 higher-level teaching assistants are expected to be trained by the end of this term to provide cover for teachers, who must get their half-day a week for planning preparation and assessment (PPA) from September.
But many higher-level staff will only be paid an improved rate for the time they actually spend on classroom cover - effectively putting them on two contracts.
Unison has said assistants should boycott the extra responsibilities if schools only pay for time spent taking lessons; they expect higher-level assistants to be paid at least pound;23,265 a year.
Jayne McGurk, who is trained as a higher-level assistant and has been at Berwick Hills primary for 15 years, said: "When we agreed to cover lessons it was on the basis that the job evaluation process would take account of our new role. But since the new pay scales have come out this is certainly not the case. It has reached the point where we feel we cannot take classes until this has been resolved."
Some staff have already been told that they will get a pay rise of just Pounds 400 a year and other assistants are actually taking a cut.
Mrs McGurk said: "We are not blaming our headteachers, who have been very supportive of us. But by taking this stance there will be no way at all that schools in Middlesbrough will be able to implement PPA time in September."
The action is not confined to the North-east. Staff in the West Midlands, Essex and London are also said to be protesting over a lack of pay to cover lessons.