A student at Lafayette Elementary School digs through her backpack during the first day of San Diego Unified begins phase one of its reopening plan at elementary schools. / Photo by Adriana Heldiz

I recently asked the head of school at La Jolla Country Day School, Gary Krahn, why he didn’t put up any plexiglass around desks. His institution, which serves elementary through high school kids, has been open since the fall.

“The science on that didn’t pencil out for me,” he said.

Instead, Krahn and the private school’s leadership focused on the air.

They put hospital-grade carbon dioxide monitors in each classroom and then hooked them all together. Now Krahn or any teacher or student can check on the CO2 levels in any classroom at any time.

CO2 isn’t the problem, necessarily, but the turnover of CO2 in a room is a perfect proxy for ventilation. If CO2 levels reach above 700 parts per million, that means people’s exhalation is filling up the room. When people exhale, they send out droplets and aerosols. The droplets quickly fall to the ground. The aerosols, though, do not. They hover like cigarette smoke.

If you have proper ventilation, if you have good air filters, the air will turn over. Fresh air is good.

Not-fresh air – air loaded with viruses hitching a ride on people’s breath – that’s how people share the coronavirus. La Jolla Country Day focused on this problem, and has had no outbreaks. Each classroom has a designated outdoor space. They’re allowed to be indoors for only 45 minutes – a schoolwide policy meant to ensure that no matter what the CO2 readings say, they’ll give the air time to turn over.

Krahn says he’s probably going to move it to an hour soon.

“I wanted to make it a bit uncomfortable so they got into the habit of going in and out – I want them to know, clearly, that it’s safer outside,” he said.

If you want to prepare spaces for people to gather safely, if you want to stoke confidence about your handle on the virus, you need to know that it spreads in the air. You address this the same way you would address cigarette smoke.

You either go outside, or you ventilate and clean the air.

That’s what La Jolla Country Day did, and now only 79 of the school’s 1,130 students have chosen to stay home and work remotely. The school’s community is thriving.

In contrast, we have now gone a year without most public schools in San Diego. Yes, teachers have been teaching, and students have been learning. But the pandemic and resulting reluctance to open in-person schools annihilated school communities, and educators, administrators and parent volunteers are exhausted trying to hold what’s left together. They’ve watched peers disappear, families move or choose private schools, teachers take early retirement.

Finally, last week, we got this: “San Diego Unified has announced plans to reopen classrooms and return to in-person instruction the week of April 12, 2021,” reads the school district’s own website.

The relief was short-lived. The San Diego Education Association, the teachers union, called that date, April 12, a “fixation” of the media and a projection that’s not set in stone.

They are in charge.

“They basically have near veto power at the local level. More than anything else, they’re the reason schools remain closed,” Tony Manolatos, a public relations professional who has a contract with the district but said he wasn’t speaking on its behalf, said of the union.

The union has demanded three things, and said only when those are met will its members be comfortable going back. That’s why the date isn’t worth fixating on, they said.

Two of the three things are on track: San Diego needs to fall into the red tier, and we need to have made vaccinations available to teachers and school staff. They’re not required to get them but they’re strongly encouraged to.

The third is going to be a tougher issue.

The union wants to see “strict onsite mitigations being in place at every school site,” according to a letter it sent to members. The district has not outlined clearly what those are. Principals across the region have no idea exactly what they’re supposed to do.

District leaders haven’t clearly answered any questions about what exactly the school days will be like, the loads teachers will carry and what adaptations for ventilation and air cleaning they have made. My wife and son and I recently took a virtual tour of a San Diego Unified school, and to assure us they were prepared, administrators showed us a picture of desks with plexiglass. A year after all this began, and we’re as far away from opening as we ever have been.

Desks at Lafayette Elementary School are adorned with plexiglass to protect students from the spread of coronavirus. / Photo by Adriana Heldiz

But we can get there. The answer is to just pretend every class has a kid smoking a cigarette. What would you do to mitigate the smell for everyone else?

You’d do a lot outside – and when inside, you’d have open windows, fans, air filters and masks. San Diego Unified’s advisers from UC San Diego emphasized the district must have “measurably excellent” ventilation. But even that group was divided about plexiglass.

“Although one expert felt barriers were useless to protect against aerosolized virus which hovers in the air, the expert in aerosol dynamics pointed out that barriers were useful when closer than 6 feet to block larger droplets such as from coughs and sneezes – drops that fall to the ground at that distance,” their report says.

The plexiglass is only good for stopping sneezes and coughs aimed right at it – the droplets will otherwise fall to the ground within six feet. That’s how the six-foot rule for social distancing arose in the first place. But if you put up too many plexiglass barriers, you actually make it more difficult for aerosols to clear out of a room.

Check out what happens with smoke if canyons form. Positive airflow toward a barrier like that leads to negative airflow on the other side.

A demonstration of aerosols traveling over barriers from Steven Jevnikar, a professor of mechanical engineering and research associate at Lawson Research Institute.

In other words, you show me plexiglass and I see potential pools of viral aerosols. The UC San Diego experts decided not to come down on either side of this debate. But my point isn’t to try to tear down the plexiglass (though districts may want to see if someone wants to buy it). My point is that the school district leaders need to muster every communication muscle they have to convey to their employees, parents and students that they understand the virus and have done specific things to deal with it.

The virus does not spread on objects. The scientific advisers warned San Diego Unified there was more danger from overuse of disinfectants than from viruses spreading over surfaces.

It spreads in the air.

From Encinitas to San Diego to Chula Vista, we have about six weeks to get this right. We can do it. Our school communities have been ravaged, but they are not dead. We have models, like La Jolla Country Day and others, that have been operating safely. And we must get it right.

The UC San Diego scientists writing to the district made sure to include a warning up high their Feb. 14 report to San Diego Unified. They considered the danger of students going back to classrooms and spreading the disease but they also considered the danger of not going back: Anxiety, depression, suicide ideation, overeating and even increased prevalence of myopia could cause irreversible long-term damage to kids.

In coming days, the district plans to ask parents if they want their children to come back. But it should hold off until it can clearly explain what it is they would be coming back to.

And it can’t be pictures of desks with plexiglass dividers.

Scott Lewis

Scott Lewis oversees Voice of San Diego’s operations, website and daily functions as Editor in Chief. He also writes about local politics, where he frequently...

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