If anyone knows how much work it takes to bring students back to school in a pandemic, it's custodian Chip Tourigny. He has been preparing South Street Elementary, a sprawling school in Fitchburg, to safely accomodate more than 600 students full-time beginning Monday.

Tape measure in hand, he was recently arranging and rearranging desks to ensure they were spaced at least three feet apart, in keeping with state guidelines.

To give students and teachers as much space as possible, some desks have been moved into the library and cafeteria. Soon more might be needed to be placed in the gymnasium, said Michelle Crowell, the school's principal.

“I don't even have an open closet at this point,” she said. “We've really tried to utilize every inch of workspace in this building.”

It's a scenario that has been playing out in elementary schools across Massachusetts, as most prepare for an Apr. 5 reopening. State officials are calling it the beginning of the post-pandemic era, but schools will look and operate much differently than they did pre-COVID. Since February, the state has allowed students to be in classrooms with as little as three feet of spacing. The Federal Centers for Disease Control and Prevention has recently adopted the same stance.

The reality is that all students couldn’t return to classrooms full-time with six feet of spacing in many schools because they wouldn't fit.

Jessica Tang, president of the Boston Teachers Union, said the city likely won't have enough room for elementary and middle school students who are scheduled to return Apr. 26.

“Truthfully, there are a lot of schools that even with three feet of social distancing, that's going to be very difficult,” she said. “There may not be enough space.”

These are some of the safety concerns that haunt educators, despite pool testing at schools, growing numbers of educators who’ve been vaccinated and masks becoming standard attire.

“There's a couple of kind of caveats to approaching this as a broad — yes, everybody can go back at three feet willy nilly," said Elissa Schechter-Perkins, a professor at Boston University School of Medicine.

Perkins co-authored a study that helped inform the CDC's decision to change its recommendation for student spacing to three feet instead of six. No difference was found in infection rates between schools that used the different standards, she said, when other key mitigation steps were taken, such as mask-wearing.

The analysis did not include schools that were fully remote, which are often in communities with high rates of infection. The research, however, did control for racial and ethnic disparities, she said, and is one of the only studies of its kind conducted in the country.

Still, the upshot is no scenario exists without risks. Perkins cites the dramatic increase of mental health problems for many students who have stayed home during the pandemic as a major health concern. But schools are not a "zero risk" proposition either, she says.

“If schools are safe, it makes sense to understand that there are going to be some minimal risks — the same way there are minimal risks in everything that we do,” she said.

Keeping these risks minimal means lots of new school rules, some onerous. Students must eat lunch six feet apart and in rooms with windows because masks will be off. They must keep a six-foot distance from teachers and face the same direction in class. The American Federation of Teachers, the national union, criticized the CDC’s recalibration to a three-foot distance, citing risks at the highest density, least-resourced schools.

But Dan Gutekanst, Needham's superintendent, said reopening full-time is a challenge even in one of the state’s wealthier districts. Some elementary schools are tight or plain overcrowded, and some staff are anxious about returning.

Gutekanst says the strict distancing stymies student collaboration but is one of the trade-offs needed in order to return to in-person teaching and learning.

“We think it's worth the trade-off,” he said. “But it's not a plan ... for the future. We really have to rethink how we can facilitate a more conducive and productive learning environment.”

As little as one foot separated many students pre-COVID, he said.

Gutekanst recently ordered $3,000 worth of “soft seats” to free up space in classrooms by allowing students to sit on the floor. One principal is considering purchasing dozens of buckets that younger students can flip over and use as portable mini tables.

Health experts, teachers and staff are meeting to discuss planning. Still, about 500 Needham students in all grades are likely to remain remote, the superintendent says.

In Brockton, about 1,500 students are currently opting for remote instruction. The state granted Brockton a delay in its return to full-time learning in elementary grades, until Apr. 26.

“Those numbers could go up,” said Superintendent Michael Thomas, of the remote learners. “I’m sure there'll be some apprehension and anxiety around coming back.”

Thomas says climbing infection rates in recent weeks have have made families wary. Lunchtime logistics are also tripping up full-time reopening. Thomas says there’s not enough room for students to eat at a safe distance, so the answer will be outdoor tents.

At South Street Elementary in Fitchburg, students already attending school via the hybrid model have been also adjusting to the new protocols. They take outdoor mask breaks to get some fresh air. They've adapted so well to wearing masks that many forget to take them off while playing “Simon Says.”

Fitchburg's rate of community infection has been high enough to push the city into the state’s “red zone" off and on. It also made headlines last fall when an outbreak at a Pentacostal church was linked to more than 200 COVID cases in 22 cities and towns.

Now the city is taking a dramatic step forward, reopening to all its students, even the high schoolers, on Apr. 5.

Superintendent Robert Jokela says he’s confident it can be done safely. Many teachers have been vaccinated. Staff have plans for every possibility. And 67 percent of families recently surveyed said they want to return. That also leaves a third who could remain remote.

“That's fine. Teachers will continue the streaming that they're doing now to students who are staying remote during our hybrid model," he said.

Kindergarteners at South Street walk through the hallways single-file with their with arms outstretched in front of them. It’s a little bit zombie-like, but teachers say it’s one way to help the littlest ones remember to stay spaced apart. Custodians with machines called foggers spray down every inch of classrooms nightly with a mist of disinfectant.

The school has been hybrid for a month, and shortly after reopening, a student tested positive for COVID. Crowell, the principal, said everyone at the school was notified, and close contacts were tested. Two close contacts were teachers who had already been vaccinated.

“It's starting to feel a little bit more, and I say it in air quotes here – "normal,’” Crowell said.