Education Minister Joe McHugh has said it is difficult to see all students being able to return to school in September if the two-metre social distancing rule remains in place.
Schools are due to reopen on a phased basis in early September, according to the Government's road map for lifting Covid-19 restrictions.
Mr McHugh told RTE radio's Today with Sarah McInerney that the Department of Education will publish a road map for the reopening of schools in two weeks.
He said: "With the two-metre rule still in place it's hard to see all students being back in September."
At the NPHET briefing on Thursday, chief medical officer Dr Tony Holohan insisted the team's advice on the recommended social distancing measure being two metres remained.
A number of sectors have highlighted the potential economic and societal benefits of a reduction.
"We're clear on the advice that we have at the moment that it represents, we think, a reasonable interpretation of the evidence and a precautionary approach to its application," he said.
"We think it's the right measure for now. In relation to every piece of advice, and not just this one, we keep all this under review."
Meanwhile, the majority of students have signed up to the Leaving Certificate calculated grades system.
Mr McHugh said efforts will be made to reach out to students who have not signed up ahead of Thursday night's 10pm deadline.
As of 9am on Thursday, 56,000 students had signed up.
He said: "I would encourage the remaining students to get going and if they are having problems they can contact the online helpline."
