1/ Highest priority for school reopening. Enforce:
-face masks at all times (everyone)
-physical distancing (limit numbers)

Though worthy, these are lower priority. Implement as time/money permit:
-wash/ hand sanitizing stations
-improved ventilation systems

Here's why... 2/

2/ Kids can be equally/more infectious as adults. Limit class size from 30 to 15, you cut infections a whopping 50%!!

That also reduces social bubble of kids, family members, workplace & more. Enough of this 120 cohort stuff, keep to 30 or less. .. 3/ https://twitter.com/sherwhizt/status/1295948165988798465

3/ Earlier thread on why young kids could potentially be *more infectious* than adults. Apart from carrying a heavier viral load (borne out by research), they spew virions that travel faster, are smaller, linger longer, & go deeper into *your* lungs...4/ https://twitter.com/sherwhizt/status/1296884307659644929

4/ Physical distancing is supported by the inverse square law. Number of virions decreases with square of distance. Double distance, particles reduced 75%. Triple distance, 89% reduction. When you cut students 50% to get twice physical spacing, you reduce exposure 75%!!
...5/

5/ Surgical masks trap ~80% virion particles, N95 ~95%. Why would any PHO recommend *against 100% full-time usage* that prevents 80-95% particles going inside your lungs?? That's a HUGE reduction in particles in a room getting to YOU with one step!!
...6/
https://smartairfilters.com/en/blog/can-masks-capture-coronavirus/

6/ Face shields/ goggles are supplemental protection to masks, & effective barrier against larger droplets of virus. Tight sealing from swim/ski goggles w/ lighter tint are ~100 effective against transmission via the eyes though. (& easy to implement)..7/ https://health.clevelandclinic.org/will-a-face-shield-protect-you-from-the-coronavirus/

7/ Barriers around desks protect passively (no further action). Face shields (at least for teachers) are quicker and cheaper to implement. Barriers supposedly allow higher class size. Argument flawed: with *more virus particles from more students*, it works against you.. 8/

8/ Washing hands & sanitizing surfaces is certainly worthwhile. But this does not reduce aerosol particles floating in the school classroom from infected kids.

Dominant mode of transmission is *aerosols* not fomites according to PHO and WHO.
...9/
https://www.publichealthontario.ca/-/media/documents/ncov/wwksf-routes-transmission-mar-06-2020.pdf?la=en

9/ Improving ventilation is huge ticket item, not just changing to HEPA filters. Fan motors must be boosted, air ducts cleaned to move more air. HVAC mods to each school might cost $100-200K, plus annual maintenance costs. And it's hard to get right even by the experts.
...10/

10/ So - we don't want to reduce infection by 80-95% w/mask mandate, yet another 50% w/smaller classes.

Instead we keep status quo: same class sizes, same or more aerosols floating in classroom. Some benefit w/better ventilation.

What is not clear to our elected officials???

I might add that all my prior tweets should not detract from additional (& necessary) strategies for: optional online learning, providing alternatives for immuno-compromised kids/parents/teachers, funding resources for special needs children.

It should be all or nothing.

This buried thread explains why I believe Dr. Henry's concern about children constantly touching masks is unfounded *when everyone in the room wears a mask*.

An asymptomatic kid touching own mask will risk infection? Spare me! https://mobile.twitter.com/sherwhizt/status/1296912252121911296