Large classes may mean more COVID-19 cases, UW study warns

As the number of students in a classroom goes up, so does the number of likely COVID-19 cases, according to a new study out of the University of Waterloo and University of Guelph.

More COVID-19 cases would bring more days lost to classroom shutdowns, says researcher

A new study from the University of Waterloo suggests that larger class sizes could result in more COVID-19 cases. (Submitted by Pamela Smythe)

A new study from the University of Waterloo suggests larger class sizes leads to more COVID-19 cases. 

The study used a mathematical model to look at how the COVID-19 coronavirus spreads within childcare and elementary school classrooms of different sizes. Researchers found that the spread of COVID-19 accelerated as class sizes increased, according to lead researcher Chris Bauch.

"When you double the class size from eight to 15 to 30, you get more than doubling in terms of cases and lost student days of classroom time," said Bauch, a mathematics professor at the University of Waterloo. The research was done in partnership wiht the University of Guelph, he said.

The results were so striking that Bauch said he's recommending parents choose remote learning this fall, if they have the ability to do so.

"It's a difficult decision, having kids myself I know that," he said. "But … especially in those districts where elementary classes will still have 30 students in a room, I definitely recommend considering the remote option."

That's the plan for parent and public school teacher Kristina Bertrand, who plans to keep her school-age daughter home.

Bertrand, who is on maternity leave, has set up a mock classroom in her front yard to prove a point about just how crowded an elementary classroom can get. She has 23 child-sized paper cutouts spread out on her lawn, which she says is about the same size as her Grade One classroom.

Parent and teacher Kristina Bertrand has set up a mock classroom in her yard to show how crowded a elementary class can be. (Paula Duhatschek/CBC)

Bertrand said she wants people to know "all the implications" of sending their kids to school, although she understands not everyone will be able to keep them home.

"There is no perfect answer," said Bertrand, who thinks the province should do more to keep class sizes small.

Large class sizes a 'triple whammy,' researcher says

The University of Waterloo study has not yet been peer-reviewed. It has been released early as part of the university's commitment to informing the national COVID-19 response, the university said. 
Mathematics professor Chris Bauch says the model suggests school boards should look for ways to make class sizes smaller. (Submitted by Pamela Smythe)

In it, researchers looked at elementary school student-teacher ratios of 8:1, 15:1 and 30:1. In the childcare model, they studied child-teacher ratios of 15:2, 8:2 and 7:3.

In both the school and childcare cases, Bauch said, the fewer bodies in a classroom, the better.

"It comes from a triple whammy," said Bauch.

He explained that the more students in a classroom, the higher the chances that one of them will test positive for COVID-19.

If that happens, a larger classroom means that more students will be affected if it's shut down due to a COVID-19 outbreak.

On top of that, Bauch explained that before a student tests positive, they will likely go through a period where they don't show symptoms.

"So by the time you've identified a positive case of COVID in the classroom there are probably others in the classroom who have already been infected, especially if you have large classrooms," said Bauch.

He noted that larger classrooms make distancing more difficult and create more opportunities for aerosol spread of the infection.

Although distancing and increased hygiene measures helped, Bauch said reducing class size had the most significant effect in limiting COVID-19 cases. 

In the childcare model, he said researchers also found that grouping siblings together also resulted in fewer cases, because there was less chance of spreading infection between households.

Bauch said he thinks the province could do more to help boards keep class sizes low. He also encouraged schools to consider creative ways of shrinking classes, such as splitting kindergarten classes into two classes of 15, rather than a single group of roughly 30 students taught by both a teacher and early childhood educator.   

Local class sizes

That's part of the plan at the Upper Grand District School Board (UGDSB). The elementary return-to-class scenario posted on the board's website said it plans to divide many large kindergarten classes into two groups.

The UGDSB said it also plans to hire an additional 60 teachers to further reduce class sizes, and will have a better idea of what class sizes will look like once all parents have confirmed if their kids will return to in-person class, or learn remotely.

The Waterloo Region District School Board (WRDSB) and Waterloo Catholic District School Board said they, too, are still awaiting final attendance numbers to determine what class sizes will look like in the fall. The WRDSB is also removing furniture to allow more distance within classrooms, a spokesperson told CBC News. 

The Wellington Catholic District School Board didn't respond to a request for comment by publication time, but said in a news release Wednesday that it wants to achieve an average class size below 22 for the board's "youngest learners."

A spokesperson for Minister of Education Stephen Lecce told CBC News the province's plan has been informed by the latest scientific and medical information. The spokesperson said the plan is a "living document" that will be augmented by expert advice as it becomes available.

Bertrand says she thinks the province could do more to keep class sizes small. (Paula Duhatschek/CBC)