President-elect Donald Trump looks on as his choice for education secretary, Betsy DeVos, speaks at a rally in Michigan in December. (Mike Segar/Reuters)

National teachers unions are mounting an aggressive campaign against Betsy DeVos, President-elect Donald Trump’s pick for education secretary, arguing that she is an ideological extremist with a record of undermining the public schools her department would oversee.

The National Education Association, the largest labor union in the nation, is mobilizing teachers to call and email their senators, urging a vote against DeVos’s confirmation. The president of the American Federation of Teachers, Randi Weingarten, is scheduled to deliver a speech Monday in which she plans to say that DeVos endangers a new and fragile bipartisan consensus on the federal government’s role in education.

“Betsy DeVos is not qualified, and even more than unqualified, Betsy DeVos is an actual danger to students — especially our most vulnerable students,” said NEA President Lily Eskelsen Garcia. “She has made a career trying to destroy neighborhood public schools, the very cornerstone of what’s made our nation so strong.”

DeVos is a Michigan billionaire and major Republican donor who, during the past two decades, has focused her energy and political contributions on promoting charter schools and taxpayer-funded vouchers for private and religious schools.

She played a key role in shaping the freewheeling charter-school sector in her home state, which even some charter supporters say lacks quality, oversight and transparency. And she has been a powerful force in pushing for new voucher programs, donating to state lawmakers who favor such programs.

She also has been openly hostile to teachers unions, describing them as standing in the way of an improved education system.

“Many Democrats love the idea of providing equal opportunity, right up until the moment when the teachers union leaders say ‘no,’ ” DeVos said in a 2015 speech.

Trump’s election — and DeVos’s nomination — have put teachers unions in a different position than the one they had hoped they would enjoy heading into the next presidential administration. After eight years at odds with the Obama administration about education policy, they had expected a closer relationship with a Hillary Clinton White House, and the unions gave Clinton early and ardent endorsements.

But instead of having the ear of the president and a stronger voice in shaping federal policy, they are now even further out in the cold, facing a prospective education secretary with whom they could not have less in common.

When Trump announced his selection of DeVos in November, Weingarten said she had “no meaningful experience in the classroom or in our schools.” Garcia said the NEA is concerned not only about DeVos’s record on charter schools and vouchers but also about how she might handle the Education Department’s civil rights enforcement responsibilities.

While the union fights DeVos and Trump in Washington, Garcia said, the NEA sees more opportunity to advance its priorities at the state and local level. The bipartisan Every Student Succeeds Act, which President Obama signed into law in December 2015, introduced new restrictions on the education secretary and handed more authority back to states and school districts.

In her speech Monday, the AFT’s Weingarten plans to laud the Every Student Succeeds Act as evidence that the country has moved past its bitter education wars, but she will say that DeVos’s ideology threatens to reignite those battles, according to a copy of her prepared remarks.

Weingarten plans to contrast the AFT’s vision for improved schools — including a focus on the mental and physical well-being of children, project-based learning and stronger teacher preparation and ongoing development — with DeVos’s record of “efforts to destabilize, defund and privatize public schools.”

“We finally reached a strong bipartisan consensus on a way forward to improve public education in America,” Weingarten plans to say. “Instead of nominating an education secretary who sees her mission as strengthening public schools and implementing the blueprint Democrats and Republicans crafted and cheered,” she plans to say, Trump has “chosen the most anti-public-education nominee in the history of the department.”