The Twin Cities German Immersion school board voted late Monday to tear down the former St. Andrew’s Catholic Church in St. Paul’s Como Park neighborhood and replace it with an 18,000-square-foot addition.

While school officials say their decision follows consideration of alternatives, including buying a nearby private school, a group of neighbors says it will continue to search for ways to save what they consider a historic thread in the fabric of the neighborhood. Designed by Charles Hausler, St. Paul’s first city architect, the 1927 building is worth preserving, said neighbor Anna Mosser.

“If we had learned this building had no significance, or did not have a significant architect, then we would have walked away,” Mosser said. “Let’s not knock it down before we know what we’re losing here.”

St. Andrew’s closed in 2011. School officials, who bought the church property two years later and extensively remodeled the church into gymnasium, auditorium and classroom space, say the decision to now raze and replace it is the best way to meet the needs of a booming school.

Minnesota’s only German-immersion school has seen explosive growth since it started with just 46 students in 2005. It now enrolls more than 500 students in kindergarten through 8th grade, and the school anticipates 100 more in the future.

“This year we had over 100 families applying for admission to next year’s kindergarten class, and the school has had a substantial waitlist for several years,” said Ted Anderson, the school’s executive director.

Without a new facility, officials said, they not only would be forced to shoehorn students into spaces that weren’t designed as classrooms, but they could wind up pushing families away. Keeping the church space would require spending about $1.2 million on a long list of repairs, including replacing the boiler, windows, doors and terra cotta roof.

The addition, which will be built on the same footprint as the church, would cost an estimated $4 million and allow the school to better serve three 24-student sections per grade, school officials said.

“Our obligation as a board is to ensure our students receive a top-rate education supported by our mission of ‘innovative education of the whole child through German immersion’, said board Chairman Sam Walling. “To that end our focus must be to do what is right for our students and staff. We empathize with the community and their long-standing ties to the former St. Andrew’s church building. However, as a public school we cannot forgo our fiscal responsibility and fiduciary duty as stewards of the school.”

Neighbors had hoped the school would buy the underused Central Lutheran School less than a mile away, possibly splitting into two campuses. While German Immersion school officials said they spent months analyzing the possibility, they rejected the idea as too expensive.

Still, neighbors say they aren’t done fighting.

A group of neighbors, Save Historic St. Andrew’s, remains hopeful that a team of historians it has hired will help prove the building’s significance.

Said Bonnie Youngquist, a leader of the neighborhood group: “If we are not going to look out for our historic buildings, who is?”