The Irish National Teacher's Organisation (INTO) has said the phased reopening of schools may not go ahead if the return to classrooms prompts a spike in Covid-19 cases.
The next stage of reopening is due to begin tomorrow, with younger students among those getting back to the classroom.
Junior and senior infants, first and second class, and Leaving Cert students will return to school tomorrow, representing approximately 300,000 pupils.
However, the INTO's general secretary, John Boyle has warned the return of the remaining class groups, which is due to take place on March 15th and April 1st, could be halted if weekly reports suggest the virus is spreading at a concerning rate through schools.
Mr Boyle said a report on case numbers in schools will be received by the union early next week, following the return of special education students to in-person classes earlier this month.
"We will be getting a report from the special classes on Tuesday and that's why we are not definite that schools will reopen on [March] 15th, because it will depend on a lot of things," Mr Boyle said.
"We will be getting those reports every Monday or Tuesday and if the numbers are spiking in the schools, well obviously the next half of reopening won't happen," he added.
Variant concern
This comes amid continuing concern regarding new variants of the virus, with one public health expert saying new variants of Covid-19 will come to Ireland very swiftly unless we take action to prevent it.
On Saturday, 738 new cases of the virus were recorded here and 13 additional death, while there are now 551 Covid patients in hospital and 132 in intensive care.
Despite gaining approval earlier in the week, new laws proposing mandatory hotel quarantine for people arriving from high risk countries will not come into effect for another week or two.
Dublin City University (DCU) Professor Anthony Staines believes the Government's response is too slow.
"The Government is bringing in mandatory hotel quarantine, but at a very leisurely pace and for a very restricted number of countries.
"We see these new variants of concern are being found everywhere, for example, there was a new variant of concern found last week, and it was found on the same day in Nigeria and the UK," Prof Staines said.
"We don't know where it came from," he added.