The National Education Association endorses Hillary Rodham Clinton on Saturday for the 2016 Democratic presidential nomination. (Melina Mara/The Washington Post)

The National Education Association, the nation’s largest labor union, endorsed Hillary Rodham Clinton on Saturday for the 2016 Democratic presidential nomination.

“We recommended Hillary Clinton on the incredible and lengthy track record she has, that is just wrapped around children, working families and education, from preschool to graduate school,” NEA president Lily Eskelsen García said.

Seventy-five percent of the union’s 170-member board backed Clinton.

The nod from the NEA gives Clinton a much-needed boost, after the International Association of Firefighters earlier this week backed away from plans to endorse her.

Before the vote, Clinton appeared before the board — at NEA’s Washington headquarters, five blocks from the White House — to make the case for their endorsement. She spoke and answered questions in a town-hall style setting for about 90 minutes, addressing various topics such as special education, standardized testing and historically black colleges.

“She knew what she was talking about,” Eskelsen García said. “You could see people sit up straighter and think, ‘Oh my gosh, she understands our world.’ I think they were simply blown away.”

But the endorsement triggered an immediate backlash among some of the union’s 3 million members. Some argued that an endorsement was premature, while others said Sen. Bernie Sanders (I-Vt.) was a better choice.

“I’m very disappointed,” said Marie Corfield, an art teacher from New Jersey, who had organized a lobbying effort against the Clinton endorsement. “I think the NEA is going to get a lot of pushback from its members over this.”

The Massachusetts chapter was among several that either abstained from voting or voted against endorsement of any candidate. Barbara Madeloni, president of the Massachusetts Teachers Association, said her members want a “real conversation about the candidates and the issues. We want to talk about the corporate reform movement that is looking to privatize education and a chance to educate the candidates about what is happening.”

In June, the Vermont NEA chapter endorsed Sanders in his bid for the Democratic nomination.

“I am proud to have the support of many hundreds of thousands of members of the National Education Association and trade unionists all across America,” Sanders said in a statement Saturday. “We are going to win this nomination and the general election because of support from grass-roots Americans. We are on track to do just that.”

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(Darla Cameron/Federal Election Commission filings)

Over the course of her public life, Clinton has received backing from wealthy supporters of charter schools, including Eli Broad, the Los Angeles billionaire; and Alice Walton, a primary shareholder Wal-Mart. And Clinton has spoken favorably about public charters, which are funded by taxpayers but run privately and are usually not unionized.

“She’s raised a lot of Wall Street money and from corporate entities,” said Corfield, who supports Sanders. “Educators are tired of being blamed, kicked down, our schools underfunded, our schools segregated, and we are tired of being blamed for all the ills of society. We want a president who is going to support free and fully funded public schools and an education workforce that’s respected. I’m not convinced that’s Hillary Clinton.”

In a statement, Clinton said she was “honored” to stand with the NEA, and she promised to back labor rights:

“I’ve stood with educators throughout my career — from my early days working at the Children’s Defense Fund to my success creating a new teacher recruitment program in the Senate. As President, I will fight to defend workers’ right to organize and unions’ right to bargain collectively, and I will ensure that teachers always have a voice and a seat at the table in making decisions that impact their work.”

In July, the American Federation of Teachers became the first national union to make an endorsement in the primary, also choosing Clinton. That sparked a backlash among some in the union’s rank-and-file, and several petitions were launched on to try to rescind the endorsement.

Both teacher unions have been under siege from elements within the Democratic and Republican parties.

The unions have been fighting the expansion of public charter schools, teacher evaluations based on test scores, and challenges to tenure and other workplace protections.

The unions have both been critical of many of the education policies of the Obama administration, saying they have led to a “blame-the-teacher” culture. They argue that evaluating teachers based on student test scores does not recognize the complexities of teaching students who often come from impoverished homes or struggle with disabilities and language barriers that affect their achievement.