At Sonoma State University, double-digit percentage increases in tuition are often an annual rite of passage.

But this week, Charles Reed, chancellor of the California State University, warned of a spike across the system, including at SSU, that could dwarf those seen over the past decade.

Tuition could jump 45 percent next year if the state doesn't extend temporary tax increases as proposed by Gov. Jerry Brown, he said. Otherwise, $1 billion could be slashed from the 23-campus system's budget.

"There are no good options, only extreme choices," Reed said. "Raising tuition is always a painful choice. But we would be faced with just trying to keep our classroom doors open."

CSU trustees already have approved a 10 percent annual tuition hike for next fall, from $4,440 to $4,884. The additional 32 percent increase that Reed warned of would take tuition to $6,450, a total increase of 45 percent from this year.

It would be more than double the tuition level of just three years ago.

"It would a huge deal," said Mackenzie Caswell, 19, a SSU human development major, who works 20 hours a week baby-sitting and teaching dance to cover living expenses while using loans to pay for school. "It would mean I'm in debt even more when I'm done with school."

"For me even a couple hundred bucks is a lot," she said.

On top of tuition, SSU students pay more than $1,275 in fees, an amount that also will go up next year with a new $300 assessment to pay for a new student center.

Many low-income students would be insulated from the potential tuition increases. About 28 percent of SSU students receive Cal or CSU University grants that likely would adjust to cover any such increase.

The rest of the student body — or their families — pay tuition and other college costs out of pocket or get loans, grants or scholarships.

While SSU traditionally attracts a wealthier demographic than most state schools, such rising costs would be difficult for many.

"I'm glad I'm graduating," said Sean McCarthy, a 30-year-old kinesiology major, who struggles to pay his tuition through an installment plan he uses to avoid taking loans. "That would be a huge jump for me."

Still McCarthy said he recently met a Berkeley student whose tuition makes SSU's combination of tuition and fees totaling $5,718 sound like a bargain. Berkeley's tuition and fees are currently about $12,500 a year.