About 40 schools across Northern Ireland could be set to close or merge, according to Education Authority (EA) plans.
The EA's action plan for 2017-18 sets out a strategy for changes to the number and nature of schools.
It identifies and names about 40 schools where "sustainability is an issue" across the 11 council areas.
One school has described the plan as being punished "for having the temerity to be small and successful".
However, any decision to close or merge schools would be subject to consultation.
'Too many schools'
The EA's director of education, John Collings, said Northern Ireland had too many schools, particularly primary schools.
"We must maximise the use of the schools' estate through sharing and co-operation to ensure that the educational experiences of our young people are the best they can be," he said.
"This will also help reduce duplication and ensure efficient use of resources."
However, some schools are opposed to any plans to merge or close them, such as Mercy Primary School in north Belfast, which could merge with Holy Cross Boys and Holy Cross Girls primary schools under the EA plan.
The financial position of a school and how many pupils it has can be used to decide if a school is sustainable or not.
Other factors are quality of educational experience, strong leadership, accessibility and strong links with the community.
Over a third (36%) of primary schools have fewer than 105 pupils, while almost half of post-primary schools have fewer than 500 pupils.
Those are the minimum numbers of pupils recommended in the Department of Education's sustainable schools policy.
In 2013, an independent panel recommended that some small schools were closed or merged.
In October 2016, the EA's draft area plan signalled that there would be an increasing number of closures and mergers.
However the action plan makes proposals for the future of a number of individual schools.
In a statement, the principal of St Patrick's College in Dungiven, Michael Gormley, said: "Governors, staff and indeed a lot of pupils and their parents are surprised that we have been selected to be included in this action plan.
"We are more than meeting the needs of the local community we serve within all legislative requirements and within a very tight budget situation.
"If the decision has been taken purely on the size of the enrolment, then it is a very sad day for this part of Ireland to be punished, by the state, for having the temerity to be small and successful.
"I am aware that there are much smaller post primary schools in our council area that have not been included in this action plan so therefore we are even more surprised that we have been selected," he added.
'Too many schools, too few pupils'
Speaking in the assembly last October, the former education Minister Peter Weir also said that there were too many small schools.
"There are too many schools with too few pupils to generate sufficient funds to deliver the curriculum to an acceptable level," he said.
"The current status quo is not an option."
The action plan was drawn up with input from Council for Catholic Maintained Schools (CCMS), and Comhairle na Gaelscolaíochta (CnaG).
The Northern Ireland Council for Integrated Education (NICIE), the Governing Bodies Association (GBA) and the Controlled Schools' Support Council (CSSC) were also involved.
It is the first Northern Ireland wide plan for future school provision.
A number of schools could also see their enrolments rise if proposals contained in the plan are followed through.