A persistent drop in private school enrollment for the last decade has compelled the closure of 17 campuses in Hawaii. Even the stronger, long-standing private academies have found suddenly the need to promote themselves, launching vigorous ad campaigns.

The enrollment decline is paired with another trend line: an upswing in student registration at the state’s public charter schools. This, parents hope, can approximate the benefits of private education, including smaller class size, without its cost.

With the cost of living in the islands continuing its relentless rise, families who in the past contemplated private schooling have taken that tuition expense out of the budget. This is not necessarily a bad sign for Hawaii education. It signals increasing competition from the charters and improvements in the performance of conventional public schools as well.

The public charters — which are financed primarily by a per-student allotment of state tax dollars, supplemented by their own fundraising efforts — have benefited and flourished, and that’s a plus for family choice in the education of children.

But it also underscores the reason why oversight, and the maintenance of standards on these fledgling campuses, are so important.

This oversight is provided principally by the state Public Charter School Commission, which reviews a charter applicant’s plans and capacity to deliver the education promised, and reassesses the charter when it’s up for renewal, or if there is a problem.

This panel has applied a more rigorous set of rules to the state’s 36 public charter schools, thanks to laws enacted more than five years ago. A series of embarrassing cases of abuse of public funds — charters that hired dubiously- qualified relatives or otherwise fell short of the standards — led lawmakers to reform the program.

Now it seems that the commission is taking a more critical approach to evaluating charter applications. In stories by reporter Susan Essoyan that appeared in Sunday’s Honolulu Star-Advertiser, Sione Thompson, the commission’s executive director, said the panel aims to “be sensitive to the need.”

This means offerings in a place where population is growing, or where a particular focus might not be otherwise available to the local community, Thompson said. That is the right strategy, one that must become even more scrupulous with a growing roster of charters.

For parents and guardians, the decision on the best educational option for their children remains complex.

Religious-centered private schools offer a specific educational content and environment that some families want; other private schools have well-established curricular strengths and a history of academic achievement that still can command a high price.

And some charters have a defined mission — such as the culturally oriented Hawaiian charter schools — that stand out for some families. Others have become true laboratories for innovation.

Finally, the public school system itself has worked to improve performance and has succeeded, by various measures, including test scores and the National Assessment of Educational Progress.

Despite its mandate to accommodate all students, regardless of ability, the Department of Education has adopted innovations and devised its own. There are the International Baccalaureate and Early College programs, as well as academies established within schools offering separate tracks. And public schools have a wider curricular and extracurricular range that round out an education.

That’s why the health of the conventional school system remains an essential goal. The flowering of the charter-school network is to be applauded, but with an eye out for any weeds springing up in the mix. Properly tended, charters bring value to a newly multifaceted scholastic scene.