Alberta Health Minister Tyler Shandro at this morning's news conference. Photo: Screenshot of Government of Alberta video

Cohorting practices as they currently stand are “insufficient” and put itinerant teachers especially at risk, said public health experts and four Ontario teacher unions at a Wednesday press conference. 

Cohorting in its current state is currently failing, said Amy Greer, a tier-two Canada research chair in population disease and an associate professor in epidemiology.

If there is any crossover between students in different cohorts, Greer said the cohorts end up being one very large cohort rather than the smaller, isolated groups they are intended to be. Students may be in one cohort with their class during the day, for instance, but are exposed to a different cohort when they take the bus home, she explained. 

The same can be said for teachers who must move from classroom to classroom, from cohort to cohort. This largely includes itinerant teachers, such as occasional or supply teachers. As has previously reported, educational assistants also travel between classes, putting themselves at increased risk of exposure.

Greer said there needs to be professional cohorting, too, so that teachers do not mingle with each other before returning to their own cohorts.

“It’s really important to consider this staff cohorting in order to reduce risk for broader spread of the pathogen within a school setting amongst staff, having staff that move between classes really be minimized, and more novel modes of delivery be considered in these types of situations,” she said. 

Susan Ursel, an employment lawyer representing the four unions in a recent complaint they brought to the Ontario Labour Board, cited one example of an itinerant teacher in a Catholic school board who tested positive for COVID-19.

“That itinerant teacher would be somebody who was exposed to and carrying with them potential exposure … as they move from school to school,” Ursel said.

“This would be an example of a failure to cohort professional staff, and to keep them in a singular school or to find other methods by which they could extend their teaching into other schools such as virtual methods.”

The press conference was hosted in the wake of an Ontario Labour Board decision to dismiss a case the four teacher unions brought to the board in August, in which the unions claimed the province of Ontario had violated the Occupational Health and Safety Act by failing to “adequately respond” to the COVID-19 pandemic in its school reopening plan.

The four unions who filed the case were the Ontario Secondary School Teachers’ Federation (OSSTF), the Elementary Teachers’ Federation of Ontario (ETFO), the Ontario English Catholic Teachers’ Association (OECTA) and the Association des enseignantes et des enseignants franco-ontariens (AEFO).

The labour board said it does not have jurisdiction to respond to the unions’ case, but Ursel labeled the board’s decision as a “narrow and meager reading of what the Occupational Health and Safety Act can do for workers to keep them safe.”

“It tells us that workplace problems in our schools must be tested one by one, classroom by classroom, without even the guidance of provincial standards as to what constitutes safety,” she added.

“This mammoth task is being downloaded on to teachers and educational workers at a time when they are already stretched thin.”

The experts at the press conference — two public health specialists and one civil engineer specializing in indoor air quality — presented a number of measures they would like to see implemented in schools across the province to reduce the spread of COVID-19.

In addition to better cohorting practices, smaller class sizes topped the list of recommendations. Without class sizes of about 15 to 20, physical distancing is not an option, said Greer, but is an important prevention measure.

Jeff Siegel, a professor of civil engineering and a specialist in indoor air quality, said that improved ventilation, filtration and overall air quality is of the utmost importance in reducing the risk of exposure to the air-borne disease.

As temperatures cool and heating systems in schools are turned on, pathogens spread more easily through the air, he said, because the moisture in droplets quickly evaporates, allowing them to spread further.

“I find it very hard to believe that we’re actually debating about meeting minimum guidelines for ventilation. In my world … no one is debating that,” said Siegel.

“In the context of infectious disease, we’ve known for hundreds of years that poor ventilation leads to increased risk of most respiratory infectious diseases,” he added.

“And we further know that there are a variety of studies that have happened over the past many decades that if we increase ventilation, we reduce the risk of transmission further.”

Dr. David Fisman, an epidemiologist and infectious diseases consultant, stressed the importance of mask wearing in schools, for all children, regardless of age. He, too, warned that the autumn season and cooler weather presents prime conditions for the spread of respiratory diseases.

“We now understand that both short and longer range aerosol transmission of the virus is likely the dominant means of transmission. Aerosols are produced by coughing, shouting, singing and even loud talking,” he said. Loud talking is, of course, commonplace in schools.

Fisman said that schools are a prime environment for spreading COVID-19, because, like restaurants, they are spaces where people have continuous exposure to one another in an indoor, crowded environment.

That said, if these measures were to be implemented, he doesn’t think schools need to shut down at this moment.

“I think we have a bunch of other levers that policymakers can pull on right now to reduce transmission in the community in order to keep schools open,” said Fisman.

Ursel said teachers and other educational workers have some options they can personally exercise to potentially improve health and safety conditions.

They can call upon health and safety reps who are deployed across school boards, she said, as well as their local union representatives who can advocate for them with their local administrators.

They could also bring shared concerns to joint health and safety committees for possible resolution, she added.

If those discussions, which involve employee and employer representatives, fall through, the health and safety representatives on the committee could call in a Ministry of Labour inspector. And, of course, teachers do have the right to refuse unsafe work, she said.

Chelsea Nash is rabble’s labour beat reporter for 2020. To contact her with story leads, email chelsea[at]

Image: Screenshot taken during this week’s press conference.


Chelsea Nash

Chelsea was’s editor in 2021. She began her journalism career covering Parliament Hill as a staff reporter for The Hill Times in 2016, while also contributing...