A number of schools have told the Department of Education they won't be able to open in time for the new term, because of works to address structural defects.
Seventeen schools have been assessed as having similar safety issues to those identified last year in 22 other schools built by the same contractor.
They're located in Dublin, Meath, Laois, Donegal, Wexford, Wicklow, Galway, Kildare and Westmeath.
The latest affected buildings were cleared for use last year - but further checks have found structural flaws requiring precautionary safety measures.
Temporary measures, including scaffolding and safety fencing are being put in place at the schools to make them safe for the coming year.
Permanent repairs are set to get underway over the summer holidays in 2020 and 2021.
Education Minister Joe McHugh says he accepts the news will anger parents.
"I can completely understand the frustration on the part of schools, patron bodies and also parents who are planning for their sons and daughters to go back to school.
"We've put a team in place - so before these investigations in the 17 schools, it will need precautionary measures.
"There was contact, physical contact, with the principals, with the caretakers to discuss a timeline".