Bosses announced yesterday that Fernhill School in Rutherglen could shortly go into administration and be forced to shut.
But last night parents confirmed they have pledged hundreds of thousands of pounds to put the school on a firm financial footing.
A statement from the board said: "We are delighted to announce the secured future of Fernhill. A plan has been put in place which will not only save the school from administration, but will also provide a platform for investment in the school's future.
"This has been possible by the swift response of parents who have secured pledges for a six figure sum.
"The reaction of the parents, teachers and pupils, when the school's future was threatened, was overwhelming and is testament to the strength of our community and the quality of education we offer.
"We look forward to continuing to offer a fantastic education to our pupils in a close and friendly environment and to welcoming new pupils next year."
The statement added: "Further financial support was also pledged by board members Tony and Kathleen Boswell."
The move comes after a meeting between parents and the board on Tuesday evening when it was revealed Fernhill, a Catholic school, had been running at a loss.
Parents also intend to establish a new board of governors with the expertise to run the school, which has 230 pupils and 40 staff, as a viable future business.
They said the rescue plan would not have been possible without the goodwill of governors Tony and Kathleen Boswell, who had invested significant sums of money into the school in recent years and have security over the land and buildings.
The pair have agreed to honour existing financial pledges to the school as well as allowing it to operate from the premises rent free for the next five years to give the rescue plan every chance to succeed. Teachers have also agreed to a pay freeze.
Speaking of the closure threat, one parent, who asked not to be named, said: "It is a real shame that this happened.
"We need a break down of the accounts and to have a thorough look through how the money is being spent and what has happened to bring the school close to administration."