Since it's an educational institution, there's some logic in giving a letter grade to Kamehameha Schools, assessing progress in its assignment: to educate Hawaiian children, using an endowment that now has topped $9 billion.

A reading of last week's Probate Court-appointed master's report suggests that a B might be awarded. Not perfect, but far better than in the bad old days in the 1980s and '90s, when the Bishop Estate treated its educational mission — handed down by its royal benefactor, Princess Bernice Pauahi Bishop — almost as an afterthought.

Others might not be so kind. This is a time when Congress is considering a requirement that colleges with large endowments spend at least 5 percent on their mission. Although that rule wouldn't apply to prep schools, it provides a context in which Kamehameha's average allotment of around 4 percent looks, well, average.

There is good reason to hold Kamehameha to a higher standard: The need is so great and time is always short. With every passing year, another age cohort of children who deserve their chance to succeed moves out of the reach of the classroom.

And the resource is, in a word, immense. The endowment — an asset exceeding the funds backing most colleges and universities — makes Kamehameha the nation's richest prep school by far. The No. 2 spot is held by Phillips Exeter Academy in New Hampshire, with an endowment of $1 billion.

In fairness, the grade Kamehameha gets should reflect the success of the schools' work as well as the cash outlay, and many of the new Kamehameha programs for extending its reach into the Hawaiian community have great potential.

There's been an admirable push to provide early-learning support to young families, an innovative program of scholarships enabling needy Hawaiian students who can't be accommodated in the three KSBE campuses to attend other private schools, support for Hawaiian-focused charter schools and work toward training more classroom support in the public schools.

But regardless of what grade anyone assigns, the assessment is clear: There's room for improvement. The school's trustees should heed the advice of the court master and look for ways of doing better, of getting more resources out to the children and families who need it, especially those yet to be touched by Kamehameha's largess.

The court master, Honolulu attorney David Fairbanks, had praise for the progress of the schools' management over the past decade, but the 99-page report included a few dings, too. He questioned, for example, the pressure placed on entities doing business with Kamehameha to donate to the Ke Ali'i Pauahi Foundation, a nonprofit scholarship fundraising arm, even with the schools' own endowment being so substantial.

And Fairbanks faulted the school's budgeting methods: Projects were penciled in according to conservative earnings projections, so when more money came in than expected, it went unspent.

Kamehameha depends on its investments to fuel its endowment. Its spending policy authorizes spending 2.5 -6 percent of its assets each year, using a five-year average of the estate's worth as the basis.

However, there is such a thing as being too careful, and it's time for the trustees to push the envelope out significantly. They say they're working on that. Next year's educational spending is likely to top $270 million, another increase.

A better measure of success is the number of students reached through its programs. When its strategic plan was approved in 2005, 22,000 Hawaiian children were beneficiaries of Kamehameha programs. That number is approaching 36,000 now, officials said, with a goal of serving 55,000 by 2018.

Kamehameha executives point out that it takes time to build capacity in many of its most promising programs. The schools want to place more literacy specialists to work in public-school kindergarten classes in Hawaiian communities, but those teachers need to be trained.

Nonetheless, the imperative to accelerate the progress is strong. There are undoubtedly other collaborations with the state's overburdened public schools that are possible.

Princess Pauahi, who left Hawai'i this legacy, would want as many children to benefit as possible, and those who serve her legacy need to make it so.