As California's budget deficit grows, so does the size of Gov. Arnold Schwarzenegger's proposed cutbacks to public education. Schools throughout the state, which already faced $5.2 billion in program cuts through June 2010, could be forced to slash an additional $3 billion to $5.4 billion, according to the governor's latest proposal.

For Oakland schools, that could mean up to $21 million — about $600 per student — in addition to the $28 million already on the chopping block, according to interim superintendent Roberta Mayor. For Mt. Diablo Unified School District, it could amount to an extra $15 million, interim superintendent Dick Nicoll said.

Since a portion of the new cuts is likely to be retroactive, some districts might have to dip into their reserves in order to balance their budgets by June 30, the end of the fiscal year.

"I can't imagine any business that could run like this," Nicoll said, noting that districts have received wildly different state revenue projections since last September. "We simply have to absorb the hits because the state can't budget properly."

Mark Coplan, public information officer for the Berkeley school district, called the latest development "outrageous." He said the 9,000-student East Bay district has already cut about 130 custodians, records clerks, food service workers and other nonteaching positions, such as the student activities director at Berkeley High School. And that was before the latest development.

The extent of the reductions called for by the governor will depend on the outcome of the Tuesday special election. California voters will decide whether to approve six ballot measures that would cap spending and extend temporary taxes among other means of narrowing the deficit. The governor has proposed $3 billion in cuts to schools if the measures pass, and $5.4 billion if they fail. Recent polls found voter support flagging for five out of the six initiatives.

Schwarzenegger's office estimates the state's deficit to be $15.4 billion — and $21.3 billion if the measures fail. Public education makes up about 40 percent of state spending, and schools and community colleges would absorb about 23 to 30 percent of the overall spending reductions, according to a spokeswoman for California Secretary of Education Glen Thomas.

"The governor has done everything possible to minimize the cuts to education, even though they are very significant," Thomas said at a news teleconference Friday morning.

As state funding grows increasingly unstable, school districts are relying on the generosity of local taxpayers. Nicoll said Measure D, a local $99 parcel tax initiative on Tuesday's ballot, if successful, will help the Mt. Diablo school district make ends meet. Coplan said Berkeley's parcel tax revenues have helped the district preserve its art and music education and small class sizes.

Oakland school district spokesman Troy Flint and others said they would be reluctant to resort to a shortened school year, as the governor proposed; they also noted that such a change, even if authorized by the state, would need to be negotiated with labor unions. "It's certainly not something we're embracing now," Flint said. "We need more instruction time, not less."

Reach Katy Murphy at 510-208-6424 or kmurphy@bayareanewsgroup.com. Read her Oakland schools blog and post comments at www.ibabuzz.com/education.