After spending millions to support President Biden and other Democrats in the 2020 election cycle, teachers unions are finding Biden to be a reliable ally as they fight back against school districts and parents who want them to return to classrooms amid the coronavirus pandemic.

Teachers unions have ramped up their political spending, increasing from $4.3 million in 2004 to $43.7 million in 2020, according to the Center for Responsive Politics.

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The teachers unions also lean heavily Democratic in their donations, including the Federation of American Teachers, which gave $2 million to pro-Biden super PAC Priorities USA Action. The Federation of American Teachers gave more than $14 million to liberal groups between 2019 and 2020. The National Education Association, another teachers union, gave more than $23 million to liberal groups during the same time period, according to the Center for Responsive Politics.

Just 2% of teachers union donations in the 2020 cycle went to Republicans, the numbers show.

Biden has said his goal is to ensure most schools are reopened for in-person learning within his first 100 days in office, but the administration's testing czar conceded the timeline may be adjusted as needed.

President Joe Biden signs a series of executive orders on health care, in the Oval Office of the White House, Thursday, Jan. 28, 2021, in Washington. (AP Photo/Evan Vucci)

President Joe Biden signs a series of executive orders on health care, in the Oval Office of the White House, Thursday, Jan. 28, 2021, in Washington. (AP Photo/Evan Vucci) ((AP Photo/Evan Vucci))

"The health and safety of students, educators, staff and families is paramount," Carole Johnson, who was picked by Biden to lead the nationwide testing program, said during a call in January. "The administration will always be honest about the challenges we face, including addressing how and whether changes in the pandemic may impact the reopening of schools or the ability of schools to reopen."

Biden is ordering the departments of Education and Health and Human Services to provide clear guidance for reopening schools and is enabling states to tap FEMA's Disaster Relief Fund to help get the doors reopened.

However, as Chicago Public Schools and the Chicago Teachers Union battled over switching to in-person learning, Biden declined to tell Chicago teachers to return to school following a union vote to defy a district order requiring educators to return to campuses in January. 

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"It's not so much about the idea of teachers aren't going to work. The teachers I know, they want to work," Biden said. "They just want to work in a safe environment and... as safe as we can rationally make it. And we can do that."

Teachers and PSC CUNY union members hold signs during a strike outside Hunter Campus High School in New York, U.S., on Wednesday, Sept. 16, 2020. Photographer: Paul Frangipane/Bloomberg via Getty Images

Teachers and PSC CUNY union members hold signs during a strike outside Hunter Campus High School in New York, U.S., on Wednesday, Sept. 16, 2020. Photographer: Paul Frangipane/Bloomberg via Getty Images

Senate Minority Leader Mitch McConnell, R-Ky., took aim at Biden on Wednesday.

"Federal funding is no obstacle here. That's more goalpost-moving. Congress has poured more than $110 billion into making education safe," McConnell said on the Senate floor. "As of last week, states and school districts had only spent about $4 billion of the roughly $68 billion we set aside for K-12 schools. That leaves $64 billion in the pipeline already."

Meanwhile, many parents are lobbying for their children to return to in-person learning as they face the possibility of completing an entire school year without entering a classroom in addition to the months they lost at the end of the 2019-2020 school year.

In North Carolina, a patchwork of school districts have returned to in-person learning, even if students are on rotating schedules that mean they spend some time in remote classes.

But many students, especially older ones, have been fully remote for months. North Carolina mom Michelle Hallas told Fox News she feels for her daughter, a senior who hasn't set foot in a classroom since March of her junior year. 

Parents like Hallas point to new Centers for Disease Control and Prevention research that found students can return to in-person learning with minimal coronavirus spread, as long as coronavirus precautions are taken.

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"It's been a year," Hallas said. "They've had plenty of time to figure out what's going to work."

Fox News' Louis Casiano and Alexandra Hein contributed to this report.