The gulf between the Philadelphia School District and its teachers widened Friday, with the union president telling members not to report to work Monday amid concerns over COVID-19 and building safety.

“There is absolutely no reason, other than sheer cruelty, to bring members into unsafe buildings Monday,” Philadelphia Federation of Teachers president Jerry Jordan said in a statement. He directed staffers to work remotely.

The standoff emerged after Superintendent William R. Hite Jr. said he expects 2,000 prekindergarten through second grade teachers to show up at schools Monday in advance of a Feb. 22 reopening for 9,000 students. It’s the district’s third attempt at reopening since the pandemic shut schools in March.

The district, in an email to PFT members Friday afternoon, took a hard line.

“If you are expected to be in your building on Monday and choose not to do so, you will be subject to disciplinary action,” Chief Talent Officer Larisa Shambaugh wrote.

» READ MORE: Philly teachers’ union says it’s ‘not safe’ to reopen schools, city to appoint mediator. Will teachers return?

In a statement, Hite said he found Jordan’s directive “deeply disappointing.”

“This is in violation of our collective bargaining agreement and the Memorandum of Agreement that PFT reached regarding the reopening of schools just a few months ago,” he said. “What is more troubling is that this action directly impacts our efforts to support the more than 9,000 pre-K to second grade families who want their children to return to school buildings for in-person learning.”

The superintendent, in an email sent to principals and obtained by The Inquirer, said he understood that some people believe it is not yet the right time to return students to schools.

“I firmly believe both that this is what our students need and that we are ready,” he wrote. “Will we be perfect in our implementation? No. We will find issues and we will then need to address them. But we must move forward together.”

The PFT president earlier this week triggered a provision in the union’s reopening agreement with the district that requires a neutral third party to judge whether the district has met health standards.

The mediator chosen by the city is Peter Orris, a doctor with a master’s in public health. Orris, who lives and works in Chicago, has begun reviewing documents, and will call the two sides together this weekend.

A city spokesperson said officials “hope the parties abide by the findings and recommendations of the mediator since this is precisely why such a provision was included in the agreement.”

Many classrooms throughout the city lack adequate ventilation, but Hite said this week that even in those rooms that have been judged through air balancing to have a safe occupancy of zero, one teacher can be inside as long as he or she is alone.

The district is spending $4 million on ventilation, including purchasing window fans for 1,100 classrooms. The fan fix, which Hite has said is just one layer of protection and a “good-faith effort,” has drawn outrage and skepticism.

Vaccines are also a sticking point. Hite has advocated for teachers to be vaccinated as soon as shots are available for them and said the district plans to organize inoculation clinics at its schools. But a return to classrooms is not conditional on vaccination, he said.

A group of 119 school nurses signed a letter to the superintendent, the school board, members of City Council, and Health Commissioner Tom Farley demanding full educator vaccination before schools reopen. School nurses have been vaccinated.

“Many questions remain, including the susceptibility of new COVID-19 variants to the vaccine, unresolved ventilation concerns, and other safety issues in our schools,” the nurses wrote. “Vaccines are not yet approved for children, and are not being offered to many of their parents, some of whom are frontline workers.”

Labor disputes have snarled reopening plans around the country. In Chicago, teachers have refused to report to buildings, and a strike is possible. In Montclair, N.J., reopening plans were also halted in January when teachers refused to go into buildings. The school system plans to sue the teachers’ union there.

» READ MORE: Window fans may be Philly’s fix for schools with poor ventilation. But teachers and parents are saying no way.

Moved by hundreds of phone calls, emails, and other outreach, some elected officials in the city called on the district to halt reopening.

“None of us takes the decision to open schools or keep them virtual lightly. We recognized that there is no substitute for in-person learning. We are fully invested in a safe and responsible reopening of school that earns the public trust and establishes clear standards for facility maintenance as well as testing and health protocols,” City Councilmembers Helen Gym, Jamie Gauthier, Kendra Brooks, and Derek Green and State Reps. Rick Krajewski and Chris Raab said in a statement.

Not getting school reopening right will mean consequences for “vulnerable communities,” the lawmakers said. “They will be borne in Black and brown neighborhoods already disproportionately impacted by COVID, by vulnerable families with chronically sick or disabled loved ones, by immigrant families terrified to access medical treatment.”

State Sen. Nikil Saval (D., Phila.) also called on the district to hold off on reopening.

“I recognize that many workers whose contributions are often unacknowledged — cafeteria workers and student climate staff — have remained in schools to distribute meals and provide support to children throughout the city,” Saval said in a statement. “But for a school to fully reopen, it is necessary at the very least for the building to be considered minimally safe for increased occupancy.”

Not a single room in Laura Wheeler Waring school in Fairmount, for instance, is fit for occupancy for multiple people, based on the district’s data.

City Councilmember Katherine Gilmore Richardson, the mother of a district kindergartner scheduled to return when schools reopen, said the district should slow its reopening plan. Gilmore Richardson said Orris’ verdict and a plan for teacher vaccinations should determine reopening.

The district’s past actions around building conditions make the public mistrustful, Gilmore Richardson said. And while virtual school is not the best learning option for most students, “putting children back in unsafe classrooms, with the risk of further disruption from COVID-19 outbreaks, will not expedite the closing of our achievement gap.”

Robin Cooper, president of the district’s principals’ union, whose members have been working in district buildings for months, believes it’s too soon to bring teachers and children back, especially given the lack of educator vaccinations and low opt-in numbers among students. At Sheridan Elementary in Kensington, for instance, just 46 of 255 eligible children are scheduled to return.

Districtwide, the families of two-thirds of the 30,000 children who could return chose not to send them back.

“No one,” Cooper said, “should be jeopardizing their own health to educate.”

A group of teachers plans to gather Monday morning outside school district headquarters to highlight safety concerns. Some will teach from outside the building.

At a recent McCall Elementary virtual staff meeting, people were in tears over safety fears, said Kaitlin McCann, of the Center City school.

“Hearing my staff’s stories, I’m going to side with them,” said McCann, who teaches seventh and eighth grade but plans to work from the School District parking lot as a gesture of solidarity. “We all want nothing more than to be in person, with our students, but we don’t want to be inside school until vaccines are distributed, until it is completely safe.”

After a busy, tense Friday and a meeting with teacher representatives from each school, Jordan said his members were “outraged and disgusted” and said he was “profoundly disturbed” by the district’s threat of discipline.

“It’s nothing short of bullying,” Jordan said Friday night, “and I won’t stand for it.”