There will not be a 'one size fits all' solution for social distancing in schools, according to the Irish National Teachers' Organisation (INTO).
According to new Department of Education guidance, social distancing will not be essential for children in the first four years of schooling.
Third class to sixth class children will be asked to keep one metre apart.
While secondary pupils are asked to keep two metres apart, if that is not possible - one metre will be sufficient.
John Boyle, General Secretary of the INTO, says this could be possible except in some circumstances:
Mr Boyle says: "Except for the supersize classes and unfortunately, we have way too many of them in the Republic of Ireland, I think it would be possible for the class to keep the social distancing so the teacher and the pupils
"In those really big classes, it may well be that some of those classes are going to have to be split and extra teachers may have to be employed, and that's going to be a big challenge.
"But certainly I would hope that most classes would return safely and fully with their peers."
Brendan Roache, Principal of Monamolin National School in Co.Wexford, says many smaller schools will not be able to have all their pupils in class at the same time under the new rules.
Mr Roache says: "It's going to be a serious challenge for us to have everybody back, it's just not going to be possible.
"I'm looking at our classrooms as it is at the moment, we are at capacity, we are struggling for space, it's a tight squeeze as it is.
"Absolutely no way we can have 100% back, looking at it now I just think that is impossible."