The INTO is warning schools won't return on March 15th if phased reopening causes a spike in Covid-19 cases.
The next stage of reopening starts tomorrow, with Leaving Cert students and the first four years of primary school going back.
Fifth years and all other primary school classes will return from March 15th, with all outstanding classes going back after the Easter break.
The Irish National Teachers' Organisation says they'll be keeping a close eye on virus cases in schools.
General Secretary John Boyle is appealing to parents not to send in children who feel unwell.