The Department of Education is looking at whether funds from other programs could be diverted to student transportation to cover an expected shortfall of about $20 million.

The DOE has warned that school bus service to most Oahu communities and to urban areas of the neighbor islands could be eliminated next school year because of a lack of funds.

It had planned to send out a memo to parents today listing the potential impacts of the shortfall, but instead "decided to hold off … in order to review and consider the potential impact of implementing internal restrictions for non-school level funding as well as repurposing other funds for student transportation costs," said spokes­woman Sandy Goya in an email.

The memo, provided to the Star-Advertiser, said that if no other funds are found, the only regular school bus service expected to be preserved on Oahu in the 2012-13 school year would serve elementary schools along the Wai­anae Coast.

Altogether the DOE estimates that without funds from other programs to cover the shortfall, service to some 25,000 students will be cut, representing about 71 percent of regular-education students who ride the school bus. No special-education bus services will be eliminated.

"It’s a big cut," said Randy Moore, the DOE’s assistant superintendent of facilities and support services. He said the memo, while based on appropriations that are not yet finalized, was meant to give parents time to plan.

"We’re telling parents because of a reduced appropriation for student transportation that we’re going to have to knock a whole lot out of it," he said.

The department is expecting a shortfall of about $20 million for student transportation in the 2012-13 school year, roughly half of what it spends on bus services for about 35,000 general-education students. Mandated curb-to-curb transportation is provided to about 4,000 special-education students.

The cost for student transportation statewide has nearly tripled in the past decade, to $76 million in fiscal year 2012, amid rising operational costs, soaring gas prices and a years-long dearth of competitive bidding among contractors.

The DOE requested $42 million from the Legislature to preserve bus transportation on Oahu and the neighbor islands. The House version of a supplemental budget bill included less than half of that, though. A Senate version includes $23 million. The budget bill is headed to a House-Senate conference.

Ann Davis, executive director of Hawaii Education Matters, an education advocacy group, said the cuts to school bus service will hit struggling families hard.