The Mercy Order is to pull out of secondary education in south Galway with the closure of Seamount College in Kinvara in three years' time.
The announcement, which was conveyed to staff and parents yesterday, has caused "considerable shock" in the community, according to Fine Gael councillor Fidelma Healy Eames.
She has urged the Mercy Order to reconsider its decision, and parents are due to hold a public meeting about the decision in Kinvara tonight.
Seamount College is an all-girls secondary school dating back to 1922.
Located on valuable coastal property in Kinvara, it has 243 pupils compared to less than 200 several years ago.
Pupil catchment extends from Oranmore, south of Galway city, to Ballyvaughan on the Clare border, and the nearest alternative school in Gort has over 700 pupils.
There was no comment from the Mercy Order on the matter yesterday.
Ms Healy Eames said she believed the school must stay open in the context of its place within the south Galway community and in the context of educational choice.
She said an ESRI report several years ago highlighted how girls performed much better academically in an all-girls school.
In a statement last night parents of current pupils at Seamount College said they were very concerned and worried about the announcement.
"We are studying the implications and will be seeking urgent consultations with all of the stake holders - the Sisters of Mercy, the staff, the parents' council, the students' council, the community of Kinvara and the Department of Education and Science," the statement said.
"We wish to make the point that Seamount College has for many years been one of the highest-achieving, non-fee paying schools in the country," the statement said.
"We firmly believe that the will, assets, infrastructure and resources are present to resolve this positively.
"We earnestly hope that all parties concerned can work together to retain and develop our school in Kinvara."
The public meeting on the closure is to be held in the college at 8pm tonight.
