The country's largest teachers' union says it can't imagine large primary school classes returning in September.
Health officials aren't expected to allow schoolchildren to go back before the summer break.
The INTO says that when they do, large classes may need to be split - half in the morning and the other half in the afternoon.
General Secretary John Boyle says it's unlikely schools will be back to normal in September:
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"The chances are that all the children, initially anyway, will not be back together in one group and that's going to pose very big challenges for the parents, for the children themselves, and the teachers."
