The country's main teaching union has said a delay in going back to school should be considered if there is a fresh Covid-19 spike after Christmas.
The European Centre for Disease Control's warned holidays like Thanksgiving in Canada and the 4th of July in the United States caused surges in cases.
It has advised extensions to school holidays or a period of remote learning in January.
The ASTI's general secretary Ann Piggott says a decision on a measure like that might be needed before Christmas Eve.
Ms Piggott said: “If countries open up quite late in December you won't see any difference for maybe three weeks. We've actually opened up very early so if we count on three weeks it will be very close to Christmas Day when our numbers might rise.”
She added: “I think it's very important that the Minister [for Education] and the Government look at the numbers and see how they are and if they're very, very high then obviously more control mechanisms need to be put in place.”
School Covid cases
She also expressed concern about how case numbers in schools are recorded.
“Officially, within schools on week 48, there were 46 school cases and in the same week in young people aged between five and 18 there were 317 cases.
“The numbers we are hearing are within school time, whereas if somebody goes to the doctor on Saturday or perhaps at 5pm in the evening, they're recorded in a different table so the numbers are quite significant.
“Teachers are still worried when they go into a classroom."
