LOS ANGELES (AP) — With state budget cuts forcing California's public universities to shrink their course offerings, earning a bachelor's degree in four years is becoming even more difficult for many students.

"One winter quarter, there were so few classes, I could only get three out of five offered," said David Allison, a senior at California State University San Bernardino. "CSU is no longer a four-year institution. It's more like a five- or six-year institution."

As the fall semester gets under way, students at the University of California, the California State University and California Community Colleges are feeling the pinch of $2.5 billion in cuts to the state's public higher education budget over the past three years.

They're taking on more jobs and loans to pay higher tuition bills and signing up for unnecessary electives to retain financial aid because courses that count toward degree requirements are full. Meanwhile, many high school seniors and community college graduates are frozen out altogether because admissions have been limited.

"You have a generally, very stressed out student population," said Parker Jean, a political science student at Santa Monica College, a two-year school.

The squeeze could get worse. If voters fail to approve Gov. Jerry Brown's November referendum to hike income taxes on the wealthy and boost the state sales tax to generate more revenue, colleges and universities will lose another $800 million, triggering more tuition hikes, enrollment freezes and program cuts.

"Without that money they're expecting in November, we're in free-fall," said Patrick Callan, president of the Higher Education Policy Institute, a think tank in San Jose. "We're on a course to make higher education out of reach."

Referendum opponents, however, say Brown is using the threat of more higher education cuts as a stick to get support for the tax plan. If Brown wanted to fund higher education, he could reform public pensions and drop expensive projects like the bullet train, said Aaron McLear, spokesman for Californians for Reforms and Jobs, Not Taxes.

"He's using students as a pawn," McLear said.

Tuition at CSU and UC has roughly doubled over the past five years. Students at UC, which serves 220,000 students at 10 campuses, pay $13,202 in tuition and fees. At CSU, which has 425,000 students across its 23 campuses, tuition and fees run $7,017.

The state's 112 community colleges have seen tuition and fees soar 77 percent over the past three years, to about $1,500 a year for a fulltime student.

At the same time, professors have been laid off, the number of classes reduced and admissions curtailed.

Enrollment at the state's community colleges has plunged from 2.9 million in 2008 to 2.4 million in 2011. This fall, 470,000 students are on waitlists for courses, the chancellor's office said.

CSU, meanwhile, closed the door on most admissions for the spring semester, shutting out 16,000 students.

As a result, more students are now choosing private colleges or out-of-state alternatives.

Daniel Allison, the younger brother of the CSU senior, just graduated from Antelope Valley Community College, but he was short two courses required to transfer to Sacramento State University. He opted to transfer to San Diego Christian College instead, paying almost twice the cost of the state school, reasoning that even if he waited to take those two courses at Antelope Valley, there was no guarantee he'd get them and he didn't know how long it would take to graduate from the CSU.

"Instead of two years, it's taking three, three-and-a-half years. It's too crowded," Daniel Allison said.

Professors say students are desperate even for a seat on a lecture hall floor.

"One student broke into tears because she couldn't get a class to meet the minimum requirements for financial aid," said Jonathan Karpf, an anthropology lecturer at San Jose State University, where his classload has increased from 40 students to 60, and he still can't accommodate the demand.

The crunch has forced some students to alter their academic aspirations.

Adriana Hubert, a senior at UCI, said she's given up her hope of complementing her psychology/social behavior major with a public health minor because the health classes are too crowded. Instead, she's focusing on simply getting a full-time course load to keep her student housing and graduate this spring.

"I think a little bit of my education has suffered, but tuition is getting unbearable," she said. "A lot of us who are seniors want to get out before the next fee increase."

Students are also frustrated with changing admissions policies. While CSU is not admitting most in-state students for the spring, it will admit non-California residents, who pay higher tuition.

Similarly, UC has allotted more slots to non-California residents for the same reason. Out-of-state UC students pay almost triple the in-state tuition rate.

University officials say the out-of-state students help subsidize in-state students, but local students say they feel betrayed.

"You're giving priority to people with more money," said David Allison, president of the California State Student Association.

Educators say they are painfully aware that students are struggling. Many schools have already dug into reserves to close budget holes, but if the November referendum does not pass, cuts will be even deeper.

"The real tragedy is all the students we're pushing out," said Brice Harris, chancellor of Los Rios Community College District in Sacramento. "November is a very critical decision point for the state of California."