The former St. Gregory’s Elementary School— which now serves as the Lower Mills campus of Saint John Paul II Catholic Academy— will begin an ambitious renovation project this winter. The capital improvements will be financed by donors who answered the call from the Campain for Catholic Schools, which raised $8.4 million for the effort. Construction will begin in earnest after Christmas.

The Lower Mills campus presently serves 300 students in grades PreK through 8. Together with three other Dorchester campuses in Neponset, Columbia Road and Mattapan, the Catholic Academy has an enrollment of 1,200 students. It is the largest Catholic elementary school in New England, according to the Roman Catholic Archdiocese of Boston.

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The renovation project at the 1915 school building will require the school to vacate the facility until the project is completed in the summer of 2015, according to a letter from administrators that was sent to parents in November and posted on the school’s website. Students in grades Pre-K through grade 2 will use classroom space in the adjacent Elizabeth Seton Academy and in a house owned by St. Gregory’s parish. Grades 3-8 will attend classes in the Regional Catholic Schools Office, which is next door to the school and was itself recently renovated.

“We can assure you of two things: the children will be safe, and teaching and learning will continue at the highest level,” said school principal George Milot, Ed.D and Sister Ellen Powers, the regional director of the academy.

“Everything will be brand new,” said Milot, who began his tenure as principal last summer. “It’s a total remodeling with an elevator being put in and there will be a new entrance, a science lab, art room, we are redoing the music room. The heating system, all the classrooms, there will be a new floor, new roof, and new masonry outside. We’ll also install new technology. We have to plan for the future.”

Bob Atchinson, Managing Director of Adage Capital Management, brought together over 125 Boston business leaders and philanthropists to raise the sum, exceeding an original goal of $7.8 million.

“This dream is coming true today because my wife, Mickey, saw the beauty and potential of this school when she began volunteering as a tutor in 2010,” said Atchinson. “With her commitment, and the leadership of co-chair Jack Sebastian, Managing Director of Goldman Sachs, and some truly exceptional volunteers and contributors, we are rebuilding this school and helping to ensure that Dorchester’s children will continue to have access to an excellent education for generations to come.”

A group of 40 volunteers descended on the school building on Monday to carry desks and other furniture and supplies to the temporary classroom space on the campus. Volunteers from St. Sebastian’s School, Oppenheimer and the Catholic Schools Office — along with many of the school’s donors— came out to assist staff and a professional moving company in the work.

“This couldn’t have been done without these volunteers,” said Milot on Monday afternoon. “The amount of work that got done today was amazing.”

“Those of us who have been working in Catholic education for a long time have learned to do a lot with very little,” said Sr. Powers. “It’s just a breath of fresh air to be modernizing.”