The Christian Brothers have said they are to close St Michael's primary school in Dublin's Inchicore due to falling numbers.
Staff and parents were shocked by the sudden decision, with many only hearing the news on the radio this morning.
A Christian Brothers representative last night told the board of management that the school was due to shut in June.
In recent years the number of pupils at the school has dropped to around 70 boys, including a number of children with behavioural problems who have been unable to find other schools.
The primary teachers' union, the INTO, has called for an immediate review of the decision.
The Lord Mayor of Dublin, Cllr Catherine Byrne, expressed concern that the closure of the school would lead to the remaining pupils attending schools outside their locality and proposed that the school be merged with another school in the area.
"A number of years ago, the CBS and the Mercy nuns from Our Lady of Lourdes National School looked at a proposal to amalgamate the two schools," she said. "I am urging the CBS school and the Mercy nuns to look again at amalgamating the two schools."
St Michael's CBS has been educating boys in the area since the 1930s.