SACRAMENTO, Calif. (AP) — Gov. Jerry Brown kicked off his campaign for tax increases at a Sacramento high school on Wednesday, warning that passing Proposition 30 is the only way to avoid billions of dollars in cuts to schools and higher education.

He stressed the part of the initiative that would impose higher income tax rates on higher-income earners. The other part would raise the state sales tax — a broader tax increase that would affect nearly every California consumer.

Flanked by students at a news conference outside New Technology High School, Brown highlighted the message that the temporary tax increases are needed to stave off deep budget cuts that could include shortening the school year by three weeks. About $6 billion in cuts will be triggered automatically if voters reject the initiative.

"This is the most critical issue on the ballot this November, other than the presidency itself, because it's about the future, it's about our kids and it's about whether California, as a democracy, can make a public decision for our schools and take this responsibility that for at least the better part of a decade has been shirked," Brown said.

"To those whom much has been given, much will be required," he said.

The income tax increases would raise tax rates by 1, 2 or 3 percent for individuals who make more than $250,000 a year. The higher rates would remain in effect for seven years.

The Democratic governor did not touch on the proposed quarter-cent increase to the state sales tax, which would be in effect for four years. Instead, he noted that California's sales tax rate would be lower than it was last year, before temporary sales tax increase enacted three years ago expired.

Critics of Proposition 30 — from Brown's political left and right — responded to Brown's kickoff event by making their strongest argument against his initiative: That it provides no new funding for schools.

Under the budget passed by the state Legislature and signed by Brown, schools and higher education face cuts of nearly $6 billion if Proposition 30 fails, a threat inserted in the state budget in hopes of securing voter support for the taxes.

If the initiative passes, the additional revenue would help close California's ongoing budget deficit and provide schools with the constitutionally required funding to which they are entitled. It also would provide guaranteed money to local governments to pay for Brown's plan that shifts certain convicts from state prison to county jails.

"He says this is about schools when we know it's not about schools," said Joel Fox, president of the Small Business Action Committee, which opposes Proposition 30. "The school boards association said that there's no new money for schools in Proposition 30. The Legislative Analyst's Office put out an analysis of the measure and said that the money goes to the general fund budget, and so the presentation is a shell game. It's built on false promises."

The governor also faces competition from a rival initiative, Proposition 38, which is funded by wealthy civil rights attorney Molly Munger. That initiative would raise income taxes on a sliding scale on nearly all income earners while sending the money directly to schools. Proponents said New Technology High School, a school that employs a collaborative "project-based learning" style, would get about $145,000 under Brown's initiative, compared with $336,000 under Munger's.

"By staging a press conference at New Technology High School today, backers of Proposition 30 are trying to persuade voters that their measure is good for public schools. It's good stagecraft, but in reality, Proposition 38 is better for public schools than Proposition 30," Nathan Ballard, a spokesman for the initiative, said in a news release.

Brown noted that because school funding accounts for more than half of the state's general fund, a budget shortfall means less money for schools. He said the $6 billion in so-called trigger cuts would hit schools and universities in the coming year even if Munger's initiative passes.

"I can tell you one thing, only this measure saves cuts this year. There's no doubt about it," Brown told reporters after his news conference. "If Proposition 30 fails, there will be a cut of $5.5 billion from the schools. It doesn't matter if all the other measures pass, that will still happen."