On Sept. 1, Lily Eskelsen García becomes president of the National Education Association, the largest labor union in the country. She was photographed at the NEA building in Washington. (Marvin Joseph/The Washington Post)

She began her career in a school cafeteria, as a lunch lady. In three weeks, she will take over as head of the nation’s largest labor union, representing 3 million educators.

Lily Eskelsen García, 59, a telegenic, guitar-slinging firebrand, has made her unlikely rise to the top of the National Education Association as the union faces the most daunting political challenges in its 157-year history. She is already fighting back with blunt talk, urging teachers nationwide to revolt against “stupid” education reforms and telling politicians to leave teaching to the professionals.

Her first priority: Putting the brakes on standardized testing, an issue she says she believes will resonate not only with her members but also with parents — important potential allies for the political clashes she sees ahead. García says that the country is in the grip of testing mania, the quest for high scores killing joy, narrowing curriculums and perverting the learning process.

“I’ll be damned if I will sit quietly and play nice and say diplomatic things about something that has corrupted the profession I love,” García said.

Stepping in as the first new president in six years, García is taking over a union that is at war with old antagonists and increasingly sparring with its longtime allies.

Lily Eskelsen greets a supporter on Election Day in November 1998. Eskelsen ran for a House seat that year in Utah, losing to the incumbent, Republican Merrill Cook. (Ravell Call/Deseret (Utah) Morning News)

While Republicans are aiming to weaken teachers unions through such policies as private-school vouchers and legal battles over dues collection, the unions are colliding with Democrats who are challenging bedrock labor rights, such as seniority and teacher tenure. High-profile Democrats — including Rep. George Miller (Calif.) and Education Secretary Arne Duncan — shocked teachers in June when they applauded a Los Angeles judge’s ruling that California’s teacher tenure laws were unconstitutional. Last month, former CNN anchor Campbell Brown organized a similar lawsuit in New York and has pledged more to come in other states.

The NEA, which represents about one out of every 100 Americans, has been increasingly at odds with the Obama administration over testing and teacher evaluations, among other issues. That tension reached a boil in July, when the NEA — historically the more reticent of the two major teachers unions — demanded Duncan’s resignation.

“I don’t think I’ve ever seen a time when conditions surrounding teacher unionism have been as threatening as they are now,” said Charles Taylor Kerchner, a professor at Claremont Graduate University who has written extensively about teachers unions.

Opponents of the unions have claimed the moral high ground, accusing the two main national teachers unions — the NEA and the American Federation of Teachers — of protecting teachers’ interests at the expense of children, accusations that have damaged its image.

Now, in steps García: a loquacious longtime resident of Utah who began her education career as a cafeteria lunch lady soon after graduating from high school.

“That’s padding my résumé,” she said dryly from her office at the NEA’s headquarters, four blocks from the White House. “I was actually the salad girl. They wouldn’t let me near the hot food.”

The daughter of a Panamanian mother and the granddaughter of a Mississippi sharecropper, García was the first in her family to graduate from college. She paid her way through the University of Utah with student loans and by singing in bars and coffeehouses, accompanied on the guitar by her first husband, Ruel Eskelsen.

Eskelsen, then secretary-treasurer of the National Education Association, at a meeting of the Utah Education Association in 2002. She is a onetime Teacher of the Year in Utah and former president of the UEA. (Paul Barker/Deseret (Utah) Morning News)

She graduated magna cum laude and earned a master’s degree before taking a teaching job at Orchard Elementary in West Valley City. Nine years later, she was named Utah’s Teacher of the Year.

“I was a very good teacher,” said García, who taught at the school for 16 years.

That same year, the teachers union was dueling with the governor over school funding. The union held a rally in Salt Lake City and invited the Teacher of the Year to speak.

García strummed her guitar and sang an original composition: “I’m-a-Teacher-and-I-Got-To-Work-In-Utah Blues.” In short order, she was elected president of the Utah Education Association.

She rose up the ranks and was propelled to the executive committee of the NEA in 1996. Two years later, García took a leave of absence to run for Congress in an ill-fated attempt to unseat a Republican.

In 2011, García’s personal life took a tragic turn when her husband committed suicide in their Washington home. She found his body when she returned from an NEA business trip. They had been married 38 years.

“Depression took Ruel the way cancer takes some people,” García said. “There are no bad guys in this, no villains. He didn’t do this to us. His sickness did this. His sickness took him away. Once you understand that, it doesn’t take away the pain, but it takes away the anger.”

She has found strength in talking. Trying to protect García, co-workers at the union wanted to post a notice that Ruel “died suddenly.”

“And I said, ‘No, you won’t,’ ” she said. García dictated a new version: “After a lifelong struggle with depression, he took his life.”

Her voice mail and e-mail inboxes filled.

“People were thanking me for being that clear and telling me their own stories,” García said. “They would tell me about their mother, or their son, or their own attempt. I knew it meant something to them that I didn’t hide this and that I wasn’t angry and I wasn’t embarrassed.”

Both her sons have struggled with drug addiction. The younger, Jared, has a lengthy criminal record, mostly for theft and burglary.

“He’s probably been in prison more than he’s been out,” said García, who adopted Jared when he was 4, rescuing him from an early childhood of abuse. “I thought: ‘I’m a great teacher. I’ve got all this love.’ But that’s not how it works.”

García pressed on. “Life is good, when you think about it,” she said.

García is as plain-spoken about her work as she is about her personal life. When she addressed the NEA’s annual convention in July, she attacked those who consider standardized tests one of the all-important measures of student and teacher success.

“It’s the testing, stupid!” García said, riffing on the slogan linked to Bill Clinton’s 1992 presidential campaign. “Better yet, it’s the stupid testing!” she shouted, calling standardized testing a “phony” accountability system that has hurt public education.

Now the NEA’s vice president, García will take over the top post from Dennis Van Roekel, a one-time high school math teacher who was decidedly more measured in his manner and speech. In her new role, García will earn an annual salary of $283,124; other compensation can add $100,000.

García also faces internal problems at the NEA, with membership plummeting more than 7 percent between 2010 and 2013 to a total of about 3 million educators.

Union officials have blamed the drop on reduced education spending, the growth of charter schools — which are largely not unionized — and the increased use of technology in the classroom.

Union members are divided over the best way to regain footing, with a more militant faction known as the Badass Teachers Association saying that the NEA has been too complacent in its dealings with the Obama administration.

“Teachers are very disillusioned with some of the things that both unions have done,” said Marla Kilfoyle, a high school teacher who is general manager of Badass Teachers, which has about 50,000 members. “But the anger toward the NEA seems to be more palpable.”

That group and others want the unions to dump the Common Core State Standards, the national K-12 math and reading standards that have been adopted in most states. But leaders of both unions remain committed to the Common Core.

“I read the standards, and I love them,” said García, who has a Common Core app on her phone.

García’s tightrope challenge is to respond to the concerns of members while offering concrete ways to improve schools that will win support from the public and repair fraying ties to longtime allies, observers said.

“As talented as she is, that’s really hard to do,” said Frederick M. Hess, a political scientist at the conservative American Enterprise Institute.

Last year, in a civil ceremony, García married Alberto García, a Mexican artist. Her Spanish is spotty and his English is minimal, but they managed to work together on a book for young adults, “Rabble Rousers,” about social-justice heroes. “I wrote it at a seventh-grade level so members of Congress could understand it,” García quipped.

García — who has written a humor column about parenting and maintains a blog called “Lily’s Blackboard” — often injects such wit into the matters she takes most seriously. She once penned a protest song about No Child Left Behind, with lyrics that included the line: “If we have to test their butts off, there will be no child’s behind left.”

She and her husband held a wedding ceremony in July before family and friends at the NEA’s convention. It was officiated by Rabbi Sharon Kleinbaum, the partner of AFT President Randi Weingarten, who also attended. García is working with Weingarten to forge more collaboration between the unions, which have frequently worked in isolation.

“Can’t you just see this scene in the made-for-TV Lifetime movie about my life?” García said.

While Alberto García awaits an immigrant visa, he’s living in Mexico and his wife lives in Washington.

That leaves her free time to concentrate on the battles ahead. The union’s presidency is term-limited to six years. As García considers the union’s challenges, she sounds every bit the elementary school teacher.

“It all comes down to building personal relationships,” she said, smiling. “Personal relationships with someone who’s not always your friend, or maybe you didn’t think could be your friend. But you try. . . . I just started. And I’ve got six years to get something done.”