Secretaries and caretakers have warned that "a lot of jobs will go undone" in schools while they are on the picket line.
An indefinite strike by more than 2,600 workers is under way.
Their trade union - Fórsa - said the action is necessary because they are being denied access to a number of entitlements, including public sector pensions.
Talks at the Workplace Relations Commission yesterday failed to resolve the dispute.
Jacinta Brady and Ger Doyle are secretaries at a school in Marino, Dublin.
Ms Brady said they just want to be treated the same as the teachers and special needs assistants (SNAs) that they work alongside.
"We want pension parity, critical illness cover, and bereavement leave. It's very simple.
"I'd say this was disruptive for schools today, but it'll get a lot worse because there are a lot of things coming in the next few weeks that will cause a lot of hassle," she added.
Her colleague, Ger Doyle, said they are looking for respect.
"We need pension parity, we work in the school where everybody else around us has pensions but we don't get access to that.
"I'd say its very difficult for the people in the school at the moment for things like answering the door, letting people in and answering the phone," she said.
Darren O'Reilly is a school caretaker in Carbury, Co Kildare.
"You can't be working 30 or 40 years and leave with nothing, especially with the cost of living right now, you could be looking at poverty down the line," he said.
"Hopefully things will run smoothly but there are bins to be out tonight and we won't be putting them out."
Ciara Delves, a school secretary in Lusk, Co Dublin, said this is a matter of equality.
"The work we do isn't just admin, it's about caring for the school, teachers, children and parents. I think it is our right to have a pension."
Dave O'Donoghue, a caretaker at a school in Mahon in Cork, agrees.
"We work alongside teachers and SNAs. They provide a public service, we provide a public service, but we get none of the benefits.
"There will be a lot of jobs that will go undone in schools.
"We don't know who's opening the schools this morning or closing them this evening. We are always the first to arrive and the last to leave," Mr O'Donoghue said.
