Classroom assistants, bus drivers, catering staff, cleaners and other support workers have today walked out at hundreds of schools.
Four of the big unions have called the action in an escalating row over pay.
It has been estimated that up to 20,000 are expected to take part in the strike.
The Department of Education (DE) said it could not afford to increase wages on its current budget.
It has been estimated that up to 20,000 are expected to take part in the strike.
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