Many of the nation’s largest school districts are approaching one year since they closed for in-person instruction and some teachers unions are pushing to further postpone a return date.

Fairfax County Public Schools, the largest school system in Virginia, was anticipating a phased-in return to in-person instruction beginning Feb. 16. Fairfax Education Association, a teachers union, said that its members were comfortable returning to in-person instruction as long as staff had received both vaccine doses, Fox 5 reported.

However, that stipulation changed. The union later said they want to delay the start date until students are vaccinated. Since children do not yet qualify to receive the vaccine, and research on the effects of the vaccine in children are not complete, that could mean several more months of virtual learning. (RELATED: Parents’ Lawyers Warn Teachers’ Union That Legal Action Will Follow If They Participate In Another ‘Union-Organized Sick-Out’)

One of Fox 5’s sources told the news station that it felt like “the goalpost keeps moving.” In nearby Washington, D.C., schools are also in a limbo between remaining closed and reopening after the Washington Teachers’ Union backed out of at least two tentative agreements to return students to classrooms, and made demands that went beyond those of the American Federation of Teachers, its national union, the Washington Post reported.

Teachers in Washington, D.C. protested over the summer and worked to convince parents returning wasn’t safe despite evidence that infections did not surge when schools reopened.

In Illinois, Chicago Teachers Union members voted to defy Chicago Public Schools’ reopening plans, refusing to return to classrooms until teachers are vaccinated. The school district, which is the nation’s third largest, was planning to welcome back roughly 70,000 students for part-time, in-person instruction on Feb. 1. In early January, the union claimed that white students would benefit more from reopening, and that the quality of distance learning for predominantly minority students would subsequently suffer. However, less than one fourth of families surveyed said they would choose in-person learning if available.

Failing to reach an agreement with Chicago Public Schools over reopening conditions this week, the Chicago Teachers Union has told its members to work from home Wednesday and prepare for a strike Thursday if city officials ban remote teaching in response. https://t.co/1s1OecvmN3

— Nader Issa (@NaderDIssa) January 26, 2021

The Chicago Teachers Union blamed the push to reopen schools on “sexism, racism, and misogyny” in a tweet that was later deleted. 

Teachers are also considered essential workers by the federal government, and many states have put that policy in place to allow teachers to get vaccination priority. In nearly two dozen states, some or all teachers are eligible to receive the coronavirus vaccine as of Jan. 25, including Washington, D.C., Illinois and Virginia, according to Education Week. However, for some districts, prioritizing teachers in the vaccine rollout may not mean schools reopening any sooner. 

Data accumulated globally has shown that infections did not surge when schools reopened. Even when community transmission was high, coronavirus outbreaks in schools were still uncommon especially if precautions were in place, according to Nature. Infectious disease expert Dr. Anthony Fauci has also recommended that schools should reopen and bars close as part of an effort to slow the spread of coronavirus while mitigating the impact of keeping children from the classroom. 

Wapo: CDC finds with precautions in place, scant spread of coronavirus in schools https://t.co/5WLVVpLk4v

— Jake Tapper (@jaketapper) January 26, 2021

President Joe Biden has pledged to reopen a majority of the nation’s schools within the first 100 days of his presidency if Congress provides funding. But 100 days means more than 3 additional months that students are kept from in-person instruction. For millions of children, especially those from disadvantaged backgrounds, the damage is already done.

School districts across the country are reporting an increase in the number of students failing classes, often from missing assignments or skipped classes. The Fairfax County Public Schools released a report in November showing that the number of middle and high school students failing two or more classes increased by 83%.

Parents have also described deteriorating mental health among students that have been learning remotely. The National Alliance on Mental Illness reports that the lack of social interaction that can negatively affect adults is also found to cause or exacerbate mental health conditions in children up to a decade later. Virtual learning has upended the critical sense of stability in children’s lives that can come from established learning schedules, seeing peers, or participating in extracurricular activities, leading to a sense of alienation among students.

For families where parents can’t work from home, even an additional month of managing childcare arrangements so that their children are supervised during remote learning time is expensive and stressful. Biden’s projected timeframe could mean that caretakers need to prolong daycare until the summer months approach, and if teachers unions refuse to return to classrooms, another school semester could be spent virtually.