Steve Waters, from LJ Hookers, said the two interested parties were New Zealanders and they were looking into all the information available on the property.
He could not say whether the interested parties were from Wanganui or out of town.
The Wanganui Collegiate School board announced on Monday that St George's School was officially up for sale by tender, with a closing date of June 20.
Speculation has been rife that the Exclusive Brethren Church was buying the school to set up a church-based secondary school.
However, Exclusive Brethren education trustee John Mason denied that had ever been mooted. "It hasn't even been contemplated at any level."
Mr Mason said senior Exclusive Brethren students were now attending a new school built by the church in Hawera, an hour's travelling time from Wanganui.
"It would hardly be efficient now to bring them back to a school in Wanganui now because it's working very well."
The church's primary school-age children were not a very large group, he said.
"So we're certainly not interested in buying a big school like St George's - we don't have that many children."
Speculation has also included that a rest home or a retirement village could be built with the school's main building set up as a care facility and small villas built on the land in front.
Speculation about off-shore interest has included a pilot training school for a major overseas airline as Wanganui airport is quiet and perfect for training young pilots.
The school buildings for sale include the main school block, former dormitories, classrooms, library, kitchen, new administration building, chapel, toilet blocks and staff living quarters.
A large in-ground pool, playing fields and tennis courts are also included in the sale.
Richard Austin had said the sale of the school was the right thing to do now. "The sale is a necessary consequence of the Government declining the St George's application to integrate."
However, Education Minister Hekia Parata declined to make any comment about Wanganui Collegiate's state integration application.
Ms Parata said she would not be making any comment about integration until August when the final decision was due to be announced.
The demise of St George's School, which opened as a boarding school in 1927, was announced in August last year.