In-School Prevention

Data to inform COVID-mitigation strategy in your school.

If he can wear a mask, so can you.
Image by Manuel Darío Fuentes Hernández from Pixabay

Yes, we’re all tired of wearing them. But they work, and the pandemic isn’t over. So put your big-kid mask on.

Droplets in the air.
Image by Tomislav Jakupec from Pixabay.

COVID-19 spreads through the air like secondhand smoke. The cleaner you keep the air, the safer everyone will be.

CDC logo.
Guidance for COVID-19 Prevention in K-12 Schools
(CDC, 07.09.2021)

The pandemic isn’t over, much as we might wish it were. I know nobody wants to hear that, but it’s true.

  • Get yourself and your children vaccinated as soon as possible.
  • Everyone over age two should wear masks inside school buildings. (If you’re wondering why vax’d people need to mask up, it’s because they can carry just as much virus as unvaccinated people if they get infected.)
  • Maintain at least three feet of distance if at all possible. If you can’t, you need to employ additional mitigation strategies.
  • Don’t forget “screening testing, ventilation, handwashing and respiratory etiquette, staying home when sick and getting tested, contact tracing in combination with quarantine and isolation, and cleaning and disinfection.” We still need all of ’em.
  • Pay attention to what’s happening COVID-wise in your community, and ramp up your mitigation if things are looking bad.
American Academy of Pediatrics logo.
Recommendations for Opening School in Fall 2021 (American Academy of Pediatrics, 07.19.21)

The AAP was ahead of the CDC in one major respect: They were first to recommend universal masking in schools for everyone over age two. Why?

“AAP recommends universal masking because a significant portion of the student population is not yet eligible for vaccines, and masking is proven to reduce transmission of the virus and to protect those who are not vaccinated. Many schools will not have a system to monitor vaccine status of students, teachers and staff, and some communities overall have low vaccination uptake where the virus may be circulating more prominently.”

Do we really need 6 feet of distance if we’re all wearing masks?
(One True Thing, 03.10.21)

Honestly, the answer is no, as long as the other safety measures are in place. For a version of this article that can be customized for your school, click here.

This Ohio district has kept kids in person all year with three feet of distancing and no in-school transmission, thanks to strict mask rules. An Indiana district mentioned in this article let kids who were between 3 and 6 feet of COVID-positive classmates stay in school – and infection rates didn’t rise.

Those stories are just anecdotal evidence, I grant you. But this study from the journal Clinical Infectious Diseases isn’t. It followed over 500K K-12 students and nearly 100K staff members for 16 weeks in the fall of 2020. All the schools required masks, and 90% of them had improved their ventilation in some way. There was no significant difference in the COVID rates between schools that kept folks at 3 feet of distance and those that kept folks 6 feet apart. NB: This study was done when the virus variants had not yet hit the US.

Should kids who’ve been 3 – 6 feet away from one another be considered close contacts?
(The Ohio Schools COVID-19 Evaluation Research Team, 01.29.21)

This report from a big consortium of universities, hospitals, and research centers says no, as long as everyone involved was wearing masks.

As they explain, “Children who were close contacts and appropriately masked had rates of COVID-19 that were similar to children with no known COVID-19 exposure in school. The COVID-19 rate in the comparison group suggests community transmission outside the school

In other words, kids weren’t getting COVID from the kids they sat next to in school – they were getting it when they weren’t in school.

Two Apps to Help Maximize Classroom Safety

How long can 15 students safely stay in a 900-square-foot classroom while masked, seated, and talking? How about 20 students in a 1200-square-foot classroom? This app, from fluid dynamics researchers at MIT, lets you input your school’s parameters to find out what works.

According to this model of COVID-19 aerosol transmission from the Max Planck Society, opening windows every hour, having everyone wear masks, and decreasing the number of students from 25 to 12 took the probability of infection in a classroom from 90% to 12%. You can enter parameters for your own rooms and see how your risk changes.

Cleaning supplies. Image by congerdesign from Pixabay
Still Disinfecting Surfaces?
It Might Not Be Worth It

“In hospitals, surfaces have been tested near COVID-19 patients, and no infectious virus can be identified. . . . because the virus is very fragile in the environment —
it decays very quickly.” (WBUR, 12.28.20)

“Hand washing is crucial . . . because surface transmission can’t be ruled out. But it’s more important to improve ventilation systems or to install air purifiers than to sterilize surfaces.” (Nature, 01.29.21)

Image by Rose Wong, NY Times; adapted from Ian M. Mackay ( and James T. Reason
The Swiss Cheese Model
Of Pandemic Defense

(NY Times, 12.05.20)

“The Swiss Cheese Respiratory Pandemic Defense recognizes that no single intervention is perfect at preventing the spread of the coronavirus. Each intervention (layer) has holes.”

But combine several layers, and you have a really good barrier. The trick is you need all those layers together, not just one.

Massachusetts General Hospital logo
MGH Covid-19 School and Community Resource Library

The mother lode of scientific resources for schools and communities, aggregated by the Division of Infectious Disease at Massachusetts General Hospital. Intended for use by school physicians. Continuously updated.

Calendar. Image by tigerlily713 from Pixabay.
New Science Suggests How to Shorten Quarantine
(Elemental/Medium, 11.10.20)

Testing upon exit of quarantine — ideally around day six or seven — is more effective than upon entry, and testing twice could make an eight-day quarantine as effective as a 14-day one.

Some 2-Week Coronavirus Quarantines Can Be Cut to
10 or 7 Days

(Boston Globe, 12.02.20)

The CDC shortened its recommended quarantine duration – not because the science has changed, but because they’d rather have people quarantine for a week or 10 days than not at all.

Risk Assessment and Testing Protocols for Reducing
SARS-CoV-2 Transmission
in K-12 Schools

The Rockefeller Foundation’s report aims to help school administrators assess the risk of SARS-CoV-2 (the virus that causes Covid-19) in their schools, and identify key considerations in developing a screening

CDC logo.
Screening After Covid Recovery (10.29.20)

Student tests positive –> student quarantines –> student comes back to school. Should this student be part of COVID screening now?
Answer: The student should be excluded from COVID screening for 90 days after the positive test.

NEA Educating Through Crisis

Information on teachers’ rights and responsibilities during the pandemic, how to ensure equity for students, and teaching skills and strategies. Also includes resources for families.

Dear Pandemic: School

A team of researchers and clinicians answers questions about Covid-19. This link goes to the school section of their website.


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