The Education Minister says children who don't wear face masks to school will be sent home.
From today, students in third class and above will have to wear masks in school.
Only students who have a medically certified exemption will be allowed attend without a face covering.
It comes as Covid cases among 5 to 12 year olds have increased by 47 per cent in the space of two weeks.
Minister Norma Foley says it's an expert-recommended safety measure.
"If you provide a medical certificate explaining the situation regarding your child, obviously they will be exempted.
"But if you do not do that, there must be clarity around this - it has to be operational, it's a safety measure.
"That will be the scenario - students who do not comply and who do not have a medical basis will be asked to stand down from school."
The Department of Education is being criticised for not speaking directly to the schoolchildren about mask-wearing.
Matt Melvin, Principal of St. Etchens National School in Westmeath, says pupils shouldn't be spoken down to.
"I think the Department are talking over and above children. There seems to be a Dickensian element of 'you must do this'.
"We should explain to children why we're doing this, and the Department need to do that. They're relying on me to do that and teachers to do that, but they need to do it."
