Ten million dollars in debt and with big plans for the future, the Academy of Holy Angels wants to sell part of its Richfield campus in a plan that is drawing fire from alumni and some concern from the city.

A developer has offered the private school almost $6 million for a strip of land along Nicollet Avenue at 66th Street for retail development. That’s about six times the assessed land value. School officials say the sale would kick-start an endowment fund, allow it to repay some debt and make campus improvements.

By late Wednesday afternoon, more than 300 people had signed an online petition opposing the land sale, saying that construction on the east lawn would ruin the Holy Angels campus, eliminate important green space and add stores to an area that already has enough retail.

“Holy Angels is a beautiful campus, because of its unique architecture and grounds,” one petitioner wrote. “There is no need for another strip mall at 66th and Nicollet. This short-term fix will destroy the ambience of the school.”

Board of Trustees member Tim Murphy, a Holy Angels graduate and father, said the school offers a quality education but needs to improve its facilities. Its atmospheric brick building, built in 1931 in the middle of cornfields and now at the busy heart of Richfield, is beloved and has been compared to Harry Potter’s Hogwarts. But Murphy said he noticed how little had changed since he graduated in 1982.

“The school wants to be more vibrant, and really needs to improve its facilities,” he said. “For the institution, if you’re not moving forward in a meaningful way, you’re moving backwards.”

Via e-mail, school President Tom Shipley said the sale would raise money that could be used to add to student financial aid and to enhance teacher compensation and curriculum.

Over 20 years, Holy Angels has collected nearly $10 million in debt because of construction on a dome and convocation center and the purchase of the school and land from the Sisters of St. Joseph of Carondelet. The school’s campus master plan calls for improvements to an athletic field, renovating a boiler plant and creating an Alumni Hall, improving outside spaces and creating a training facility for athletes.

Income from the sale also could be used to create a foundation for an endowment fund, officials say. Now, the school only has a pool of restricted funds.

The possible development would use 1.7 acres of land on the campus’ eastern edge, which is less than 10 percent of the entire campus. It would include what the school describes as a “low-profile” retail space that would partner well with a high school, perhaps including a “Walgreens-like drugstore,” a coffee shop, a bank, a sandwich shop and a frozen yogurt store.

Drawings show retail buildings pushed back from a promenade that would lead to the school’s east door. The school could veto tenants, and the architectural style would blend in with the campus, Murphy said.

Though the school’s east lawn is not used often, it’s where events like the prom’s Grand March and graduation ceremonies take place. Murphy said there would be enough lawn left for those events.

Maureen Davy Tesch, president of Holy Angels’ Alumni Council, called the land sale “a bold idea.” She is trying to be open-minded but said the idea of stores in the green space is hard to swallow.

“I think it’s the retail portion that people are struggling with,” Tesch said. “I would like to see them explore other options, like a capital campaign.”

School officials will discuss the proposal with the Richfield City Council and the Planning Commission at a Nov. 26 study session. John Stark, Richfield’s community development director, said the city knows only the basics of the project, which would be across the street from the Hub.

“It’s all very conceptual at this point,” he said. “One concern we have is that the Walgreens is at the Hub. The Hub is kind of a landmark in Richfield; it’s been the primary retail center in Richfield for more than 50 years.

“We want to make sure that whatever happens at Holy Angels or anywhere else doesn’t negatively affect the Hub, or Richfield generally.”

The Holy Angels property is zoned institutional. Developing it would require an amendment of the city’s comprehensive plan as well as a zoning change.

Holy Angels’ board is expected to make a decision on the land sale by the end of the year.