(CNN) The federal government's push to reopen schools while Covid-19 is still widespread is meeting tough resistance from powerful groups with deeply personal interests: teachers and their unions.
Across the country, in New York, Los Angeles, Chicago, Florida and Michigan, teachers have united to voice their concerns with reopening plans -- and in some cases filed lawsuits or taken steps to go on strike.
The US Centers for Disease Control and Prevention, meanwhile, has issued guidelines explaining how schools can potentially return to in-person classes this fall if coronavirus case counts are low enough.
And the American Academy of Pediatrics has urged districts to return to in-person classes, citing potentially devastating social and emotional losses to children if schools don't reopen.
Parents find themselves stuck between a rock and a hard place, struggling to juggle jobs and child care yet anxious about whether their children can be safe in the classroom.
The reopenings come with widely acknowledged risks, particularly in places with high community spread of Covid-19. And nearly 1.5 million teachers are at higher risk of serious illness if they contract coronavirus, because they suffer from health conditions such as diabetes, heart disease or obesity, or are older than 65, a Kaiser Family Foundation report found.
Teachers across the country are now being forced to make agonizing choices between doing what they love and earning a paycheck, or running the risk of being exposed to the virus by students and other school staff.
And so far, their unions have been among the most important voices pushing back against reopening.
"The bottom line is that we still haven't contained community spread," American Federation of Teachers President Randi Weingarten said in a statement last week. "We don't have the necessary safeguards. And we don't have the resources to fix either. That's why more and more schools are opening remotely."
In New York, Los Angeles and Chicago, the nation's three largest school districts, the teachers' influence has been clear.
United Teachers Los Angeles, which represents teachers in the the Los Angeles Unified School District, said in July that schools should remain closed during rising coronavirus infections and deaths.
"We all want to physically open schools and be back with our students, but lives hang in the balance," UTLA President Cecily Myart-Cruz in a statement. "Safety has to be the priority. We need to get this right for our communities."
The school district had not at that time clarified its plans for the fall. But days later, LAUSD Superintendent Austin Beutner announced that schools would not open for in-person instruction when the school year begins.
Chicago Public Schools had previously announced a plan to open the school year with a hybrid learning model with both in-person classes and remote instruction.
However, Covid-19 cases have consistently risen in Illinois over the past two months. Two weeks ago, a source close to the Chicago Teachers Union told CNN that the CTU planned to convene their House of Delegates early next week to discuss taking a strike vote to demand remote learning for Chicago Public Schools.
A day later, Chicago Public Schools announced a change: they would be going fully remote for all students for at least the first quarter of the school year.
New York City schools, the nation's largest school district, are preparing to teach more than 1.1 million students with a hybrid model in which students can attend in-person classes a few days a week.
The exact plan remains unclear just weeks away from the scheduled September 10 start. On Wednesday, the president of New York City's teachers' union said no adult or child should be allowed into a New York City school building without proof of either a negative Covid-19 diagnostic test or a positive antibody test.
Mayor Bill de Blasio has not agreed to that plan, but on Thursday, the city announced a "Back to School Pledge" outlining all the steps they are taking to keep students, teachers and families safe from coronavirus.
"We are going to make sure these schools are safe and ready, and if we don't think they're safe and ready, they won't open," de Blasio said.
The Florida Education Association, the state's largest teachers' union, filed a lawsuit last month seeking to overturn the state's emergency order to open schools for in-person instruction.
Attorneys for the plaintiffs presented their case in a virtual court hearing on Wednesday. James Lis, a biology teacher at Dr. Phillips High School in Orlando, testified about his plan to resign rather than risk exposure to Covid-19.
He said he's been teaching for 21 years and lives at home with his wife and 81-year-old mother-in-law. During training this week, leading up to school reopening, he was given a face shield, a container of wipes, and a gallon of hand sanitizer.
"If there's no change, I am going to explain class by class to my students that I cannot return," he testified. "I can't put my mother-in-law at risk. I do not feel that I will be safe."
The president of the Florida Education Association, Fedrick Ingram, announced the suit against Gov. Ron DeSantis, Florida Education Commissioner Richard Corcoran, Miami-Dade County Mayor Carlos Giménez, the Florida Department of Education and the Florida State Board of Education.
Corcoran had issued the emergency order in early July, requiring all "brick and mortar schools" to open "at least five days per week for all students."
Ingram told CNN at the time that Covid-19 was spreading widely among children under 18, and argued the executive order was reckless, unconscionable and unconstitutional.
"No one wants to be back in a classroom and reopen our school more than educators," Ingram added. "But we want to do it safely. And we don't want to put people at risk."
A union representing teachers in Detroit has voted in favor of a potential strike to push school officials to make changes to the district's reopening plan.
The Detroit Federation of Teachers, which represents teachers in the Detroit Public Schools Community District, announced Wednesday that 91% of its members voted to authorize the union's leadership to launch a "safety strike" in the future.
Negotiations between the union and Michigan's largest school district began after school officials approved a reopening plan in July.
The plan included online learning, "smaller in-person class sizes and daily safety protocols such as thorough cleaning, wearing masks and social distancing," the district says.
After it was approved, teachers argued that in-person learning would put their health and their students at risk due to the ongoing pandemic.
"If we go online now and remain safe, we will be able to safely return to our classrooms and stay put in the building rather than risk outbreak, after outbreak, after outbreak," a teacher said in a video posted online that details the union's concerns.
Wednesday's vote is not "a work stoppage," the union said in a statement, adding that members have agreed to teach and work remotely.
"The action we took today is not an action we wanted to take but an action we had to take. It is not an action that we take lightly," union President Terrence Martin said Wednesday.