Saint Francis School will see its last all-girls class graduate this month, 87 years after the school was founded in Manoa.

Next month, when Damien Memorial School holds its annual summer orientation for new students, girls will be in incoming classes for the first time in the school’s 50-year history.

The milestones are being marked by Hawaii’s private-school community as something of an end of an era for two campuses that built their brands on single-gender education.

"Most of the alums would rather have us be all-male," said Bernard Ho, president of Damien. "But times have changed, and we have to change with it."

Damien’s transition to coed leaves just one all-boys school in Hawaii: Saint Louis School, which shares a campus with Cha­mi­nade University.

There are four all-girls schools on Oahu: Sacred Hearts Academy, St. Andrew’s Priory School, La Pietra-Hawaii School for Girls and Hua­kai­lani School in Kailua.

For Saint Francis and Damien the move to coed was in large part spurred by financial considerations. Enrollment at both schools had been declining for years. Saint Francis, which started admitting boys in 2006, was facing the possibility of closure.

The other single-gender schools appear to be on surer financial footing and haven’t indicated publicly any plans to go coed.

Still, Saint Louis President Walter Kiri­mi­tsu said it is a constant struggle to keep enrollment up, not least because the applicant pool for single-sex schools is, by definition, half that of a coed school. The economic downturn also hasn’t helped any.

"There’s always conversation about the possibility of going coed," Kirimitsu said, adding, "We are determined to continue as an all-boys school."

Enrollment for next school year at Saint Louis is expected to be about 600 to 650 for grades 6 through 12, about the same as this year.

Saint Louis got about three students in 2011 who transferred from Damien after the school announced it was going coed, but isn’t expecting any more in the coming school year.

Nationally the percentage of private schools that admit only girls or boys has remained relatively steady over the past decade, according to U.S. Department of Education statistics.

In 2010 about 2.4 percent of all private schools were all-boys and 1.9 percent were all-girls.

There remains a hot debate on whether single-gender education actually provides any additional benefit for students. Some researchers contend, controlling for socioeconomic status and the rigor of programs, student achievement is not higher in single-sex schools overall.

But proponents of single-gender education point to research that shows girls in all-girls schools are more likely to take traditionally male-dominated subjects — such as high-level math and physics — and that boys are more likely to explore foreign languages and music.

Ruth Tschumy, a former longtime teacher and administrator at La Pietra, said the point of single-gender schools is not to separate girls from boys, but to differentiate instruction, taking into account the different way girls and boys learn and respond to teachers.

"There is a wealth of research that shows gender-specific education is beneficial, particularly for girls," she said. "But just putting boys and girls in separate classrooms is not what single-gender education is all about. If teachers don’t employ differentiated instructional practices — gender-specific teaching — then an all-girls or all-boys school loses its advantage."

Jennifer Grems, director of the upper school at St. Andrew’s Priory, said an all-girls school allows girls to be the "focus of our attention."

St. Andrew’s Priory will remain a single-gender school, she said.

"Our girls are the opinion leaders and the star athletes," said Grems, whose own daughter attended the school. "This is where they’re empowered to believe they can do anything."

The school has about 400 students in kindergarten through 12th grade.

For Damien School, going coed was a controversial move that received initial push-back, especially from alumni.

But Ho, its president, said many parents appear to have embraced — or at least accepted — the idea.

Enrollment at the school, with grades 6 through 12, is expected to shoot up next school year to about 450, from 370. About 60 of the incoming students will be girls, who are being admitted to grades 6 through 9.

Donna Marcello will send her daughter to Damien as a freshman next school year. Her son is a junior there.

She said she supports the school’s move to coed, but said her son and his friends were initially put off by the change.

"All they know is all boys. Their first reaction was to not like it," she said. "As time went on, I think they’re getting used to it."

Marcello said that Damien already puts together a host of coed activities for students, such as dances. "Coed learning, I think, would probably be a good addition to what they have now."

Damien administrators have been preparing for the addition of girls to the campus for months.

Girls’ bathrooms were put in. A girls’ locker room is being installed. Additional coaching and other staff were hired. "Young women" was added to the school’s mission statement, and its Latin motto "viriliter age" is now translated to "act courageously" from "act manfully." (Both are correct.)

For Saint Francis the transition to a coed school —and the addition of elementary grades and a preschool — was relatively smooth, with a few bumps, administrators and students said.

"Change is hard," said Sister Joan of Arc Souza, head of school at Saint Francis, adding that a few of her teachers have left over the years because the school started admitting boys.

Saint Francis went coed and began adding elementary school grades six years ago, after weighing several options aimed at boosting enrollment. The school also considered moving its campus to Leeward Oahu.

Boys were initially admitted to lower grades. That allowed the then-seventh-grade-through-senior classes to remain all-girls.

Today those seventh-graders are the seniors.

And on May 27 all 53 members of the school’s last all-girls class will receive their diplomas. For only the third time in the school’s history, they’ll wear white graduation gowns. (Seniors also wore white for the school’s 50th and 75th anniversaries.)

At the school Monday, students said the graduation of the last all-girls class will be bittersweet.

"It’s kind of sad, but it’s good to see a change and it’s a change for the better," said senior Peyton Coro­nas, adding the final all-girls class has become incredibly close.

Enrollment at the school is now at 502, the highest in the school’s history and up from about 430 in 2006.

While boys are still the minority on the campus, they’re gaining in numbers and now make up about half of students in some grades.

Souza, who has led Saint Francis for 21 years, said the addition of boys to the campus has changed its feel. It doesn’t seem as quiet, she said. "It’s alive," she said. "There’s never a dull moment."

Junior Justin Layco, 16, transferred to Saint Francis last year from Damien. "It was a big change," he said. There are about 20 boys in the school’s junior class of about 80 students. The girls, he said, "keep us in line."