Casey Mellon, 19, didn't think a faculty strike would actually happen until two weeks ago when she was in her pop-culture writing class at West Chester University.

"My professor ran into our class 10 minutes late and had made another syllabus entirely, threw out our old one and was like, hey, this is real," said the sophomore English and secondary education major from Abington. The new syllabus shortened a project and moved up the due date, she said.

Since then, it's only become more real.

The Pennsylvania State System of Higher Education and its faculty union are locked in another round of marathon negotiations that began Friday and are due to continue through Sunday - a last-ditch attempt to reach an agreement and keep classes going for the system's 105,000 students.

Kenneth M. Mash, president of the Association of Pennsylvania State College and University Faculties, said that absent a deal, the 5,500-member union will strike at 5 a.m. Wednesday, likely bringing education to a midsemester halt at the 14 state universities: Bloomsburg, Cheyney, Clarion, California, East Stroudsburg, Edinboro, Indiana, Kutztown, Lock Haven, Millersville, Mansfield, Slippery Rock, Shippensburg, and West Chester.

"I'll either have a tentative agreement in my hand or a picket sign," said Mash, a political science professor at East Stroudsburg.

Because it would be the first strike in the system's 34-year history, questions are swirling on campuses across the commonwealth: How much time could be missed before the semester would be rendered void? What happens to students due to graduate in December? Will any classes be held? What about sports? For many of those questions, there are no firm answers.

Students interviewed last week at the student center at West Chester - with 17,000 students, the largest university in the system - were worried.

"I heard if we lose two weeks, the entire semester could be thrown out," said Matthew Bonham, 21, a junior computer science and psychology major from York.

That hasn't been determined, said Kenn Marshall, a spokesman for the state system.

The actual point when the semester would be lost and students' financial aid affected isn't clear, he said. The system must meet standards to keep accreditation, he explained.

"There is a finite time frame there somewhere," he said. "It hasn't been determined yet what that is."

If that point were reached, he said, students would get a tuition refund.

"We will do everything we can to make sure students can complete their semester in a timely manner and receive full credit for their work," he said.

Holding weekend and evening classes and cutting into semester break would be some of the options after a strike, Marshall said.

"Weekend classes, I would be extremely furious if that was even a possibility," said senior David Argust, 22, a communication studies major from Scranton, due to graduate in December. "The only people who are really getting hurt are the students."

Taylor Stenroos, 21, a junior, sympathizes with faculty but is frustrated at the prospect of being shut out of classes.

"You pay all this money to be here," said the English major from Emmaus.

She could understand a few days to force an agreement, she said, but nothing extended.

Mellon is worried that the campus could become chaotic if students are idle with no classes. The system intends to keep campuses open, including residence halls and dining facilities, and run extracurriculars when possible.

"To be honest," she said, "I'm a little fearful."

A strike likely would cancel most classes. The system has no plans to bring in replacement workers, Marshall said. But he also said it's impossible to know how many faculty would come to work.

Union officials doubt there would be many.

"They have to cross a picket line, which involves looking your colleague in the eye and saying, 'I'm willing to work and let you shoulder the burden,' " said Mark Rimple, a music theory composition professor and president of West Chester's union.

It's unclear whether sports could continue. The system's coaches, who are in a separate bargaining unit, haven't set a strike date, but trainers are in the faculty union.

Faculty and administration remain divided over work rules, health-care coverage, and salaries.

The system maintains that faculty are well-paid, their wages ranking at or near the 90th percentile nationally among similar state universities in the country, citing a salary survey published in the Chronicle of Higher Education. The starting salary for a full-time instructor is $46,609, with the top of scale $112,238 for an experienced full professor.

Nearly half of all full-time faculty earned more than $100,000 last year (including extra pay received for summer school and other duties), Marshall said. Less than a fourth of the system's managers and executives earned that much, he said.

The system has offered faculty raises ranging from 7.25 percent to 17.25 percent over a four-year contract that would cover 2015-16 retroactively and run through June 2019. (Faculty at the top of the salary scale also would get cash payments in two years of the pact.) But Marshall said the system, which faces a deficit, must get savings in health-care coverage, and faculty haven't been willing to make those concessions.

A strike, Marshall has said, could prove fatal for some of the universities already struggling with enrollment loss. The system has lost 12 percent of its enrollment since 2010.

Faculty, Mash said, are more concerned about the work-rule changes than they are about the economics of the system's proposal. The system wants to cut sabbaticals, do away with a system fund for professional development, increase hours that counselors spend with students, and make work-rule changes regarding adjunct faculty, distance education, and research.

He called Marshall's salary figures "distorted," maintaining that many faculty have doctorates and have been working in the system for more than 10 years. Hiring has slowed, so there are fewer junior faculty, he said. He also said much of the pay raises would be given back in health-care concessions.

Students say averting a strike is paramount.

"It screws everyone over, kind of," said freshman Kevin Singer, 18, of West Chester.