TORONTO — Teachers will not be at greater risk of contracting COVID-19 than other front-line workers as long as they strictly adhere to the newly issued guidance on managing outbreaks in schools, Ontario's top doctor said Thursday.

Dr. David Williams said teachers must wear masks, stay home if they're sick, wear gloves, and practice hand hygiene and physical distancing.

"We want them protected," he said. "By doing what you need to do every time, all the time ... you will not be at risk. It's a virus. It's droplet spread. It doesn't happen by magic."

His comments follow the release Wednesday of the province's COVID-19 guidance on how to prevent and handle outbreaks in schools, which critics said failed to address concerns about class size at the elementary level.

Williams said problems occur when people get "casual" about following public health rules either at work or in their personal lives.

"We don't want anyone to get infected in the schools," he said. "But we're going in fully prepared to look for it, seek it, find it, test it, and to affirm and rule it out as quickly as we can."

The new guidelines emphasize prevention, with parents asked to screen their children daily for COVID-19 symptoms and keep them home if any are discovered.

Premier Doug Ford said Thursday that the new guidelines are asking parents to do their part to keep the virus out of schools.

"I think it starts at home, the responsibility," he said. "If your child is showing any symptoms, please go to your local physician ... or get your child tested."

Teachers and principals will be asked to isolate any child that develops symptoms at school and send the child home when a parent can pick them up.

Public health officials will be given discretion to send entire cohorts of students home from school, or potentially close schools, if they feel that is the best way to manage an outbreak.

School boards, teachers' unions and some parents have called for smaller class sizes to encourage physical distancing at the elementary level. They want the boards to hire more teachers and lease additional spaces to create new classrooms.

The new guidelines do not cut or cap class size.

University of Toronto professor Charles Pascal, who once served as a deputy minister of education in Ontario, said the government's new guidance misses the mark and it's causing more stress for students, parents and teachers.

He said the Progressive Conservative government could make better use of the hundreds of millions of dollars the province is receiving from Ottawa.

"With the new money from the federal government, they refuse to spend it all on the safest choice: smaller elementary classes that require many more teachers and more ventilated space," he said.

The president of the Ontario Secondary School Teachers' Federation said the guidance is vague and does not indicate clear lines of responsibility, which means some duties could fall by the wayside.

"I think this is a sign of the complete mismanagement of the Ministry of Education, by the minister, they're scrambling," he said. "They don't know what they're doing. They don't have time to do things properly."

The president of the Ontario English Catholic Teachers' Association said putting precautions in place to make schools safe is key.

"The Ford government says they will spare no expense to keep schools safe, but Ontarians have not seen this yet," Liz Stuart said in a statement. "We need them to live up to their word by putting in place the same standards around physical distancing, hand sanitation, and ventilation as are expected elsewhere in the province."

Both unions said they were not consulted by the government in the creation of the new guidelines.

Colin Furness, an infection control epidemiologist at the University of Toronto, said he's concerned the guidelines don't take into account the asymptomatic spread of the virus.

Health officials should focus on risk-based testing in schools, as opposed to symptom-based testing, he said.

That could include things like testing teachers twice a week and distributing saliva-based tests for families to use at home, he added.

"This (guidance) is written out of an obsolete textbook," Furness said. "It's not incompetent, it's inappropriate."

Meanwhile, Canada's largest school board said elementary students will be able to opt-in or out of in-person classes at three points during the academic year — on Oct. 13, Nov. 23 and Feb. 16, 2021.

The Toronto District School Board said the deadline to request a move will be set approximately two weeks before each date.

The board says it's not possible to switch immediately because of the impact that would have on staffing, physical distancing and space allocation.

Ontario reported 118 new cases of COVID-19 on Thursday and one new death related to the coronavirus.

This report by The Canadian Press was first published Aug. 27, 2020.

Shawn Jeffords, The Canadian Press