At Evelyn Gonzalez’s Denver high school, the Italian teacher, who luckily speaks Spanish, filled in recently for the Spanish teacher, who was out sick for two days.

So many students were absent from Haven Coleman’s history class at another high school that the teacher held off on teaching the day’s lesson rather than have to repeat it later for the missing kids. Coleman’s class had a study hall instead.

In Carbondale, an entire grade level at Crystal River Elementary switched to remote learning, not because teachers were sick, but because several of them were also parents of preschool-aged children quarantined at home.

If this past fall felt “mostly normal,” Assistant Principal Kendall Reiley said, then after winter break, “it felt like we were coming back into a different world.”

January’s massive COVID-19 surge has tested pandemic-weary teachers, students, and families in new ways, with half-empty classrooms, missing teachers and abrupt temporary switches to remote learning, often for just a number of days.

The lack of substitute teachers is a major problem. In District 11 in Colorado Springs, almost half of teacher absences went unfilled earlier this month. Many districts are dispatching central office workers, many of whom were never teachers, to help at schools. Denver sent out 500 of them a day, prioritizing coverage for schools at risk of closing.

Some teachers and students have said a short period of remote learning would provide more stability and question whether the disruption involved in keeping schools open is worth it. Amber Elias, Denver’s lead operational superintendent, believes it is.

“As much as our primary purpose is instruction, we provide so many more benefits,” Elias said. “I keep going back to the research that shows students are physically, mentally, and emotionally safer in school. We would rather keep kids in school when we can. We know we are not able to provide that quality of instruction that we would at full staffing, but there are a lot of other benefits to school.”

District leaders statewide have mostly kept buildings open amid case rates that would have shuttered them a year ago. They cite the availability of vaccines, plus widespread concern about the toll virtual learning took on children’s mental health. Relaxed safety protocols are also giving schools new tools to stay open, like combining classes and shortening quarantine.

That doesn’t mean this month has been easy. Some students say they’re worried about catching the virus but also dread a return to virtual schooling.

“Going remote learning is like going a step back to the past,” said Andrew Caballero, a sophomore at Denver’s Abraham Lincoln High School. “Students should be able to go to school and interact with other students and not be home 24/7.”

For Shane Knight, principal at Denver’s Knapp Elementary School, the text messages start at 5 a.m. and go until late. At first, he and his assistant principal were keeping track of sick or absent teachers on a whiteboard, marking those who were out with COVID-19 with a red “C+.”

They later moved that accounting to a spreadsheet, but the logistics of who was absent and who was covering their classes became so unsustainable that Knapp temporarily switched to remote learning, one of more than 45 Denver schools to do so by the third week of January.

“As soon as I informed my staff, the tension in the building dropped dramatically,” Knight said. “It was palpable. They were on edge like, ‘Who is leaving next?'”

It’s a feeling teachers from across Colorado said they know well.

Cara Godbe teaches a combined second and third-grade class in Montrose. Vaccination means some students who would have had to quarantine in the fall can now stay in the classroom, but that presents its own challenges.

“I might have eight kids who are eligible to stay in the classroom, and 16 that are not,” she said. “And that puts teachers in a bind. How do you teach both groups of kids?”

When the third-grade teacher at Kate Tynan-Ridgeway’s school, Palmer Elementary in Denver, was out with COVID-19 right after winter break, she and the other second-grade teacher split his class, adding 10 more kids to each of their rooms.

Instead of teaching the regular second-grade curriculum, Tynan-Ridgeway said, “I was inventing my whole day. It was like, ‘Let me adapt this. Let me adapt that.'” Though the students were still getting academic instruction, it wasn’t what they’d normally learn.

The next week, Tynan-Ridgeway had to miss school because of her own COVID-19 exposure.

It’s hard to get a clear picture of school closures because Colorado doesn’t track them. Some districts reported that student and staff absences were similar to those in the fall when Colorado endured a prolonged delta wave. Other districts reported a dramatic increase in cases, lower attendance and teachers out sick.

The Adams 14 district in Commerce City went remote the second week of January but opened most of its schools later in the month. Bayfield in southwestern Colorado canceled all classes and activities in mid-January after a fifth of the entire teaching staff either tested positive or entered quarantine.

Jason Hoang, a senior in Aurora, decided to quarantine after finding out that a friend tested positive for COVID-19. The quarantine wasn’t required, but Hoang felt it was the right thing to do. Some teachers offered him a way to participate in classes remotely, but others just gave him assignments to do on his own at home.

“I’m surprised we’re actually still in person considering how COVID-19 numbers have skyrocketed,” Hoang said. “I prioritize safety. I wish the school did that as well.”