The pending sale of a property that includes Portland’s Catherine McAuley High School has prompted its trustees to explore relocating the 45-year-old Catholic girls high school.

John Wasileski, a developer of senior housing in southern Maine, is close to completing the purchase of the 12-acre property on Stevens Avenue that houses the school, as well as a former convent for Catholic nuns. Wasileski said Monday he plans to renovate the 200,000-square-foot convent, called the “mother house,” and eventually build additional housing on the 12-acre site.

Although the sale would not directly affect Catherine McAuley’s lease, it has prompted school officials to consider their long-range plans.

“This is a great opportunity to take stock of where we are and where we can go in the 21st century,” said head of school Kathryn Barr. “McAuley is more than just an address, but we want to do what’s right for our girls and for the future.”

McAuley’s lease is good for at least another five years, which gives a recently formed committee of trustees time to look at other real estate and buildings where the school could be housed.

Heidi Osborn, who chairs the board of trustees, said the board members have often thought about what might happen if the school had to relocate, but that it was never an imminent possibility.

“I’m not even sure I know how challenging this might be, but for us the most important thing is to have a facility that works for the girls,” Osborn said.

Wasileski believes the school could continue at its current location and coexist with the senior housing project, although construction of the additional housing would eat into athletic fields on the site.

“No one wants them to leave,” he said. “We consider them an asset and we hope they will stay as part of the grand plan.”

Wasileski’s company, Seacoast Management, signed a purchase-and-sale agreement in June with the property’s owner, Sisters of Mercy – Northern Community, the regional offices of a Catholic women’s organization that operates hundreds of schools and nonprofits across the world.

Wasileski has already built two large senior housing complexes – Ocean View in Falmouth and the Highlands in Topsham.

The sale of the property on Stevens Avenue has not been finalized, but Wasileski is expected to go before Portland’s planning board next month to discuss the project.

“The final sale is contingent on a lot of financial pieces, such as (obtaining) historic tax credits, but I’ve had my eye on this for at least 10 years,” he said. He would not reveal the purchase price.

The sale also was contingent on making sure the school would not be immediately displaced.

Catherine McAuley High School was established on its current site in 1969 after the merger of St. Joseph’s Academy and Cathedral High School.

The Sisters of Mercy own the property, which abuts Baxter Woods, and has leased it to the school for the last 4 1/2 decades.

Enrollment at McAuley, Maine’s only remaining single-sex school, consistently topped 200 students in the early part of the last decade but has dropped since the 2008 recession. The school now has about 150 students, Barr said.

“We want to stay small but could certainly accommodate more students,” she said.

Osborn agreed that enrollment levels are where they should be and said any new facility would not expect any dramatic increases or decreases in the student population.

“It’s such a great community. Nobody gets lost in the shuffle,” she said.

If the school does end up moving, Barr said it would almost certainly remain in Portland.

Whether or not McAuley moves, Wasileski has big plans for the property, although he said they won’t happen overnight and that the timing will be dictated largely by the market.

He plans to renovate the convent into approximately 80 apartments for low- to moderate-income seniors. The building also has a former chapel in the center that will be converted into a common area.

On the undeveloped side of the parcel, which includes the athletic fields being used by the school, Wasileski plans to build a retirement community of apartments and condominiums that could house another 175 to 250 residents. Those buildings, he said, would be built based on presales, which means construction would not happen all at once.