Schools across Northern Ireland are facing major disruption and possible closures on Thursday as thousands of non-teaching staff go on strike.
Classroom assistants, bus drivers, catering staff, cleaners and other support workers are walking out at hundreds of schools.
Four of the big unions have called the action in an escalating row over pay.
A representative from one of the unions said 15,000 to 20,000 are expected to take part in Thursday's action.
The Department of Education (DE) said it could not afford to increase wages on its current budget.
Officials said they would need extra funding to do so and were working with the Education Authority (EA) to try to resolve the matter.
The Education Authority said it expected "significant disruption" to schools on Thursday, in areas such as transport, school meals and cleaning services.
It would also have a "major impact on the availability of classroom assistants in schools".
The unions said there had been a failure to implement a long-standing review that would lead to pay increases.
