Even as the Philadelphia School District plans to bring some children back to classrooms after Thanksgiving, Superintendent William R. Hite Jr. said Wednesday it’s unclear whether the majority of district students will be able to return at all this school year.

A day after disclosing plans to let as many as 32,000 of the district’s youngest children return to class two days a week, if they opt in, the superintendent said there was no set timeline to resume classroom instruction for most third through 12th graders. Those plans, he said, will be shaped by COVID-19 infection rates, the state of school buildings, and public health officials' recommendations.

At a news conference, Hite said he hoped to restart in-person instruction for the first time since March, but it was “equally feasible” that it won’t occur at all this school year.

The superintendent’s plan drew mixed reaction.

The head of the teachers' union said he saw no evidence schools would be ready for tens of thousands of students and staff. Some worried about ventilation in aging buildings and weren’t sure they were ready to send their children back. Others were furious about the lack of a concrete timeline or commitment to bring other students back.

And the plan is not final. Hite needs the school board’s approval; his first reopening plan, unveiled in July, was withdrawn after skepticism from teachers, parents, and board members.

The news comes as schools across the country grapple with how to safely return students to in-person learning, as virus numbers rise locally, and with the school district already $70 million into COVID-19 expenses.

Philadelphia’s slow phase-in to in-person instruction begins Nov. 30. If all goes as planned, students with complex special needs would return in January and ninth graders and students in career and technical education programs would come back by early February.

There is no timetable for when the remainder of the district’s 120,000 students might return.

The goal, Hite emphasized, is to get children back to face-to-face learning, especially given the needs of the district’s students, the majority of whom live in poverty.

“Children learn best when they are in a classroom with a great teacher,” said Hite. “We also know that the lack of in-person learning options disproportionately harms low-income and minority children, whose families are far less likely to have the resources to hire additional child care or instructional help while they work.”

Though Philadelphia has no immediate plan to return most students to school, other districts around the region and across the country have already begun to do so. New York City’s public schools, the nation’s largest system, have reopened, though some have had to close again because of virus spikes. Miami students have also returned; Chicago and Los Angeles have not yet fixed dates for return.

In Philadelphia, families can choose to keep their children learning completely virtually, but those who want their prekindergarten through second graders learning in buildings must notify the district by the end of the month. Those who make no selection will default to remaining in all-remote learning.

For those in schools, masks will be required, and social distancing observed. Parents will be encouraged to temperature-check students at home; those checks will not happen at school.

Much remains up in the air.

Whether schools can manage in-person learning depends on teacher availability and how many families choose a fully virtual option; if large numbers of teachers receive medical exemptions to teach remotely or a majority of families at a school decide to keep their children at home, a hybrid model might not work at a school, district officials said.

To date, about 300 teachers have applied to work remotely citing medical reasons, the district said, but more are expected to apply. Teachers who work with children in pre-K through second grade are expected to return to buildings Nov. 9.

The goal is to keep children with their current teachers, but that may not be feasible in every case. Officials said they would observe current class-size limits.

The district has spent $6 million to equip classrooms with technology to allow teachers to livestream lessons so they can teach in-person and virtual learners simultaneously. Altogether, it’s spent or committed to spend $70 million on COVID-related expenses, chief financial officer Uri Monson said.

Complicating the reopening picture is the massive job of readying 200-plus school buildings for safe occupancy in a pandemic. There is significant community skepticism at the district’s ability to do so, but Hite promised vigilance and increased cleaning.

“We will not return them if in fact it’s not safe for students and staff,” the superintendent said. “Even after we return, we will not remain in school if it’s not safe for students and staff.”

Building conditions are the main concern of the Philadelphia Federation of Teachers, union president Jerry Jordan said. Years of inadequate supplies, delayed repairs, asbestos, lead, and other environmental concerns have made his members wary.

“I have no evidence that schools will be ready,” said Jordan. The union was consulted as the plan was developed, Jordan said, agreeing with school system leaders on provisions for protective equipment and social distancing. It did not have final say over other elements of the proposal.

Clarice Brazas, a teacher at the U School in North Philadelphia, said classroom ventilation is an issue; prior to COVID, many classroom windows did not open. District officials have said repairs are being made and studies are being conducted to determine how many people can safely fit in classrooms.

“Ventilation is a concern on a good day in the School District of Philadelphia, much less during COVID,” said Brazas.

Meanwhile, district officials said many parents with child-care needs are eager to return their children to classrooms, but others said they aren’t ready.

Kaija Sannicks, whose 4-year-old attends prekindergarten at Mifflin Elementary in East Falls, is doing her best to engage her daughter with remote learning, but it’s a challenge. Still, she’s not comfortable sending her back into a classroom.

“It doesn’t make any sense to me to bring those children back first,” said Sannicks. “I love my baby, but she’s not going to keep that mask on all day. … And what happens if she goes to school with someone whose parents were exposed to COVID?"

Two of Sofia Cavicchia’s teachers at Central High School told her Wednesday they don’t expect to see most students back in school at all this year. One wept as she told her seniors, Cavicchia said.

“It’s hard, because so much is up in the air,” she said. “We want to know, are we going to have an in-person graduation? Are we going to be able to step in our school one more time? There are no simple answers, no one knows, and that’s just the facts of life right now.”

That children might not return angered parents like David Knoblock.

It ignores “every bit of available evidence from around the world that schools are safe for children and teachers,” said Knoblock, father of two children at Masterman. “This policy will make the existing inequities even worse for kids and long term will damage public education.”