The national debate about teacher tenure is the focus of a trial set to begin Monday in a fifth-floor Los Angeles courtroom, pitting a Silicon Valley mogul with a star-studded legal team against some of the most powerful labor unions in the country.

The central question: Should it be easier to fire teachers?

David F. Welch, a 53-year-old founder of an optical telecommunications manufacturing firm, is challenging tenure, seniority and other job protections afforded public school teachers under California law.

He says that those policies allow the state’s worst educators to continue teaching and that those ineffective teachers are concentrated in high-poverty, minority schools, amounting to a civil rights violation.

His challenge is aimed at a core mission of the labor unions that represent 400,000 educators in the state: to protect jobs. It also sets up what could be a lengthy, expensive — and perhaps nationwide — fight over employment practices for teachers, which date back more than a century.

At the center of the conflict is the role of teachers and whether tenure hurts or helps public education. Educators, policymakers and labor activists are closely watching the case, and Welch’s legal team already has spoken with groups in New York and elsewhere about launching similar challenges outside California.

Backing Welch are some of the most incendiary players in the national argument over the future of public schools, including Michelle Rhee, the former D.C. schools chancellor who got rid of tenure in the District in 2009 and went on to form an advocacy group aimed at eliminating it across the country. Parent Revolution, the group behind the controversial “parent trigger” laws, is another supporter.

Welch has hired a team of prominent attorneys, including former U.S. solicitor general Ted Olson and Theodore Boutrous, who most recently paired to win a U.S. Supreme Court decision that struck down California’s prohibition against same-sex marriage. Welch has created a nonprofit group called Students Matter and has engaged a California public relations firm with a roster of celebrity clients.

The defendants in the case, which include Gov. Jerry Brown (D) and other state officials, have been joined by the California Teachers Association and the California Federation of Teachers.

For the unions, the Students Matter lawsuit poses a serious threat to tenure, which was first adopted by New Jersey in 1909 to protect teachers from firings based on race, pregnancy, politics or other arbitrary factors such as clothing or appearance. It has remained one of the most attractive benefits of the profession.

“Tenure permits a teacher to teach the curriculum that’s appropriate for students, without worrying that a member of the board of supervisors or board of education is going to have a different view about subjects like Islam or climate change and decide to get rid of the teacher,” said James Finberg, the lead attorney representing the unions. Tenure also makes teaching attractive to people who would otherwise seek higher-paying careers, he said.

But recent research on the importance of teacher quality has led Welch, Rhee and others to argue that tenure is an obstacle to removing bad teachers from the classroom. In states such as California, there are so many legal and procedural hurdles before a tenured teacher can be fired, they say, that it’s difficult to shed even the worst teachers.

Under California law, school districts have about 18 months after a teacher is hired to award tenure. That is not enough time to make a valid decision, the Students Matter complaint argues. The complaint also attacks seniority rules and “last in, first out” policies, which say the newest teachers are the first to be laid off when jobs are cut, regardless of performance.

Since 2010, Republican governors and legislatures across the country have been trying to eliminate or weaken teacher tenure laws. The California unions have staved off attempts to change the laws through the legislature, leading Welch to try his hand through the courts.

For the trial that begins Monday, both sides have lined up more than 100 witnesses, including some of the nation’s most lauded academic experts — among them a MacArthur Foundation “genius” — as well as superintendents, students and parents. The trial is expected to take at least a month.

Students Matter is using a novel civil rights approach, arguing that poor and minority students in California are being denied their right under the state constitution to equal access to public education, because they are more likely than affluent white students to be taught by “grossly ineffective” teachers.

“There are bad lawyers, bad journalists and bad carpenters,” Olson said. “And there are bad teachers. No one should have to spend a year in a classroom with a bad teacher.”

The lawsuit does not address the thorny issues of how to fairly evaluate educators and how to identify a “bad teacher.” Policymakers have been struggling with that challenge for years and still haven’t figured it out.

Eric Heins, a third-grade teacher and vice president of the 325,000-member California Teachers Association, said that eliminating tenure is a way to lower labor costs. “They want to create a cheap and easily replaceable workforce that is less unionized and easily fired if they create trouble,” he said.

Labor activists say that the Students Matter case is part of a broader assault on unions, as government workers make up more than half of the nation’s union membership.

“There’s been a well-funded effort these last few years to go after public-sector unions and teachers’ unions in particular, to scapegoat educators and their unions for the problems in public education,” said Joshua Pechthalt, a former high school teacher and president of the 75,000-member California Federation of Teachers.

Troubles in California’s public schools are a result of years of sharp cuts to funding, layoffs and the elimination of vital services, Pechthalt said. The state was ranked 39th in per-pupil spending when compared with other states in 2011-2012, according to an annual National Education Association analysis.

Students Matter is “playing off real concern that exists, but they’re trying to divert attention away from the fundamental problems — poverty, the lack of resources, the conditions that make it difficult for kids to come to school ready to learn,” Pechthalt said.

Katharine Strunk, an expert in teachers unions at the University of Southern California at Rossier, said that if the unions lose in court, they still may be able to maintain some job protections by negotiating contracts with local school districts. “This may change their ability to affect policy at the state level, but I don’t think it’s the death knell for the unions,” she said.

The plaintiffs in the case are nine students who say they were trapped in classrooms with “grossly ineffective teachers” who could not be fired because of the job protection laws.

“I know first-hand what kind of impact having an ineffective teacher can have,” said Raylene Monterroza, a 16-year-old high school junior who blames bad teachers in her Pasadena fifth-grade and ninth-grade classrooms for why she is now two years behind grade level in math. “I’ve had teachers that didn’t even show up to school, and when they’re at school, they don’t really care. They don’t teach anything at all.”

Another plaintiff, Daniella Martinez, is the daughter of Karen Martinez, a member of the Alum Rock Board of Education and an employee of Rocketship Education, the California-based chain of charter schools that plans to open eight D.C. schools within five years.

John Deasy, superintendent of the Los Angeles Unified School District, is among the first witnesses scheduled to testify on behalf of the plaintiffs. Deasy has said that it takes years and costs an average of $500,000 — and sometimes millions of dollars — to terminate a tenured teacher. More frequently, he said, the district has paid off the teachers to get rid of them.

That’s a result of poor management, not unfair laws, said Finberg, the lawyer for the unions. “If a particular student gets a teacher that’s not the best in the school, that’s not a decision made by the statute, that’s made by the principal,” he said.

Well-run school districts do not view job-protection laws as a problem, Finberg said. Los Angeles has increased its teacher-

dismissal rate dramatically, firing 10 teachers in 1999, and 99 in 2012, he said. “They didn’t need the statutes to be changed,” he said.”What they needed was better management.”

Whatever Judge Rolf Treu decides in Superior Court is likely to be appealed to a higher court, and a final resolution could take years, both sides say.

“I can’t imagine this not moving forward in the appeals process,” said Pechthalt, the union president. “This is a critical issue. There’s a lot at stake.”