What are the barriers that keep families from enrolling their children in preschool? Cost is certainly one of them: The University of Hawaii Center on the Family puts the average annual tuition for full-time preschool enrollment at $9,500 a year, or almost $800 a month.

But there are others. Despite the expansion of a public preschool program that is free to all participants, some of the space is going unfilled. There needs to be better outreach to communities, promoting the well-documented benefits of early learning to more families whose children could benefit most from having this advantage.

As students headed back to classes on Monday, new prekindergarten programs have opened this academic year at five public elementary schools: Kalihi Uka and Kailua on Oahu, Kilohana on Molokai, Kohala on Hawaii island and Kula on Maui. That makes 24 public preschools established under the supervision of the state Executive Office on Early Learning.

This is the state’s current effort to reach the goal of universal preschool education for Hawaii’s children. The campaign got its first big push in 2013 by the administration of then-Gov. Neil Abercrombie.

Abercrombie had hoped to enroll up to 17,000 4-year-olds in the program by reserving $32.5 million in state funds to be spent over two years, covering tuition largely in existing private preschools. This is still the most efficient way to spread the taxpayer dollar the furthest, which is key, given the competing demands for public money.

However, the state Constitution prohibits the expenditure of state funds on private schooling, and an effort to pass a constitutional amendment in the November 2014 balloting failed.

Meanwhile, the state pushed ahead with the early-learning mission and the executive office, originally under the governor’s supervision, was then administratively attached to the state Department of Education. Lauren Moriguchi, its director, said Early Learning has its own governing board but works with the DOE to see that its program meshes well with the K-12 grades curriculum.

Moriguchi said the goal is to maximize the reach of prekindergarten by expanding carefully — making sure there’s quality so the children get the best academic boost possible.

There is an application process that aims to find new participating schools where the school leadership shows commitment and willingness to carry out the early-learning training for its teachers, she said. The agency also looks for areas where the need is greatest.

For now, the emphasis needs to be on getting the word out to school communities about the program that exists and work to resolve impediments. Funding has limits, so it falls to the state to make the best use of available resources.

Kalihi Uka now has a waiting list of students, the result of school staff going door-to-door to reach families. That appears to be a successful approach that other schools might try — especially in areas where there is high enrollment of Micronesians or other groups without an early-learning cultural tradition.

Communication is a challenge, Moriguchi said: Many parents have multiple jobs and simply don’t get word the program is available. There is information online (earlylearning.hawaii.gov/eoel-public-pre-kindergarten-program), or by calling 586-3811.

Early Learning and the public charter schools, some of which offer federally funded preschool, plan to jointly advocate for legislative prekindergarten support; this seems to be a smart strategy.

But officials also recognize, correctly, that the state must revisit the notion of leveraging public funds through private preschools. Hawaii still stands alone as a state that rejects this idea. If the state wants anything approaching universal preschool, that position must change.