Roscrea's Cistercian College, which was set to close in 2018, will remain open after an action group set up to save it raised around €1.5m to secure its future.
Last month, the Co Offaly college at Mount St Joseph Abbey announced it was to close after 112 years due to a significant decline in student numbers.
The Save Cistercian College Action Group, which was set up to reverse the closure decision, also put forward a plan whereby the college will now accept day borders and five day borders.
The school previously only accepted seven day boarders.
The plan was accepted by the school's board of trustees.
The action group, which is comprised mainly of parents and past pupils, raised around €1.5m after their four-week campaign to stop the closure.
That money was pledged by donors for capital investment to develop facilities at the school.
The action group, also set up an online survey, and has received over 500 expressions of interest from new pupils planning to enrol at the school.
Action Group Chairman Ronnie Culliton said: "We are looking to the future with great enthusiasm now. This is a wonderful place for young men to be educated, play sport, develop musical talents, and grow friendships that will last a lifetime.
"We are delighted that we can now offer this fantastic opportunity to receive an education grounded in the Cistercian ethos to a greater number of families".
Last month, the school, run by the Order of Cistercians of the Strict Observance (Trappists), said a significant fall-off in student numbers was the main reason for the initial decision to announce the closure of the school.
The school had a 45% drop in enrolment in the past ten years with nine first-year students enrolled for September 2017. The school currently has 167 pupils.
There are currently five religious-run Catholic schools in Ireland that offer boarding facilities, compared to more than 30 such school in 1990.
Dom Richard Purcell, Abbot of Mount St Joseph Abbey said: "This is one of the most joyous days in the history of Cistercian College. We have witnessed a small miracle over the past four weeks.
"The decision to close was an extremely difficult one for the monastic community to make and so we are understandably overjoyed to now be in a position to announce that the college will remain open," he said.
"We have been truly overwhelmed by people's generosity which has ultimately resulted in ensuring the financial viability of the college in the immediate term.
"The hope now is that we can continue this positive work together to ensure that Cistercian College can remain open for a very long time to come," Dom Richard concluded.
Cistercian College is one of two boys' boarding-only schools in the country.
Past pupils of the college include former taoiseach Brian Cowen and former tánaiste Dick Spring.