A $6 million grant to Punahou School, expected to be announced Tuesday, will be used to fund another decade of academic programming for a public-private partnership in its 10th year of grooming disadvantaged public school students for success in college.

Every summer since 2005 the private school has welcomed a cohort of public school students following their fifth-grade year as so-called PUEO scholars. The students, who are nominated by their elementary principals, commit to an academic enrichment program of intensive summer school courses and mentoring for seven years until high school graduation.

"I just believe that we have a responsibility to make all schools better, not just Punahou, and that’s what led to this partnership," said Punahou President Jim Scott, who attended the school on scholarship. "We had to think about what do we do well, and that’s getting students ready for college."

PUEO, an acronym for Partnerships in Unlimited Educational Opportunities, is scheduled to receive the gift from the Clarence T.C. Ching Foundation at an event Tuesday at the Hono­­lulu campus. The grant builds on a $3 million investment the foundation made in 2009.

"It’s unprecedented," said Suzanne Sato, Punahou’s director of foundation relations. "In the fundraising field it’s very, very difficult to find a stable base of support beyond a pilot phase and be able to count on it. To know the support will be there for another 10 years is even more amazing."

The PUEO program boasts a 99 percent high school graduation rate for participants — most of whom graduate from public schools — and an 84 percent college enrollment rate, exceeding the state’s 82 percent graduation rate and 63 percent college-going rate for all public school students.

Punahou — the second-largest private school in Hawaii, with 3,750 students and annual tuition of $20,700 — works with 20 Oahu public elementary schools that nominate a total of 40 students a year who have to meet income and academic requirements.

Because the program follows each student throughout his or her schooling, it has students in more than 60 schools, including on the neighbor islands and mainland.

To be eligible, students must participate in their school’s free or reduced-price lunch program. Under federal guidelines a family of three cannot earn more than $42,106 a year to qualify for the reduced rate, while a family of three earning $29,588 or less qualifies for free meals.

Students also have to be performing in the academic middle of their class, meaning they cannot be in the top 20 percent or bottom 20 percent academically.

"The academic middle is very broad, but it means that we’re hitting the demo­graphic that doesn’t necessarily get services as defined by the (state Department of Education) — whether it’s super-high gifted and talented, accelerated, advanced placement — or student services that we as a private school just are not equipped to provide," said Kylee Mar, assistant director of the PUEO program.

The summer school courses, often taught by current and former public school teachers, are designed to expose students to learning opportunities they normally wouldn’t experience. For example, courses include a flight class called Up, Up and Away; an integrated performance project that involves writing and producing a play; and core classes in leadership, mathematics and language arts.

Yuna Martin, who participated in the program for seven years before graduating from Kalani High School in 2012, credits the program for giving her the motivation and confidence to pursue a college education.

"For me, personally, it is a program that has inspired me to have dreams about going to college and investing in my education," said Martin, 20, who is studying psychology at the University of Hawaii at Manoa. "It’s given me the fearlessness to go after the things that I want."

Martin said she and her brother were raised by their mother, who came to Hawaii from Japan and spoke little English.

"Job prospects were hard, especially with two kids. We were on welfare, we lived at the YMCA and on other people’s couches," she said.

Despite the hardships, she said, the program instilled in her a passion for learning.

"Yes, the tangible goal is finishing high school and college, but I think another philosophy that PUEO strives for is just a passion for learning and that no matter what background you come from, you are worth the investment, worth exploring your curiosity … that through an enthusiasm for learning you can achieve," she said. "It gave me a huge attitude change."

Mar and program director Carl Ackerman said one of the biggest challenges has been establishing trust with public school partners. Some initially criticized the program as a handout; others accused Punahou of trying to recruit student athletes away from public schools.

Critics also said the program would help widen the divide between achievement at public and private schools in a state with the highest rate of private school enrollment in the nation.

About 1 in 6 school-age children in Hawaii attends a private school, compared with fewer than 10 percent nationally. The rate more than doubles in urban Hono­lulu, where nearly 38 percent of kids are enrolled in a private school.

"I think imbued in the culture of PUEO is that we don’t see ourselves as helping out a system that needs help," Ackerman said. "We see ourselves partnering with a system so that everyone can move together, and that’s a really significant ideological difference, because I think that public education is here to stay."

Mar added that the program does not promote admission to private schools.

"Their job is to be that culture of change for their peers," she said of PUEO scholars.

Scott, whom Ackerman credits with the vision behind the program, wants to see the effort replicated to reach more students.

"This is about more than just Punahou and about more than just the Clarence T.C. Ching Foundation," Scott said. "This is about public and private schools working together for the future of Hawaii’s children. Over time we’d like to see to what extent this can be replicated and scaled."