TORONTO -- An East York elementary school where there are more than two dozen COVID-19 cases will remain closed this week.

In a letter sent to parents on Wednesday, the principal of Thorncliffe Park Public School said the closure will allow Toronto Public Health to continue their investigation into the outbreak.

The school was set to reopen on Thursday but will now instead welcome back students on Dec. 14.

"While most students will be able to return on that date, a small number of classes will not be returning until Tuesday or Wednesday as per the self-isolation letter they would have already received from TPH," Principal Jeff Crane said.

According to the TDSB dashboard, there are 31 active cases among students and staff at the school as of Wednesday.

Last month, voluntary asymptomatic testing at Thorncliffe Park Public School unearthed 19 cases.

Three teachers at the school walked off the job last Thursday, hours before the TDSB announced it was closing the school due to the rising number of cases.

Two other schools in the Thorncliffe Park community -- Fraser Mustard Early Learning Academy and Marc Garneau Collegiate Institute -- are also experiencing COVID-19 outbreaks.

On Monday, new Toronto Public Health screening guidelines came into effect to curb the spread of COVID-19 in schools.

Students who are experiencing even one symptom of COVID-19 must self-isolate along with their siblings and get a test before returning to the classroom.

Meanwhile, TDSB teachers and education workers wrote a letter to the province on Wednesday, calling for all classes to be moved online for the first two weeks in January to ensure that schools do not contribute to the post-holiday spread and prepare for more school-based, voluntary asymptomatic testing.

However, a spokesperson for the minister of education insisted that schools remain safe spaces for learning, saying that "cases are overwhelmingly not being transmitted within our schools – the risk remains from our community."

-- with files from and CTV Toronto staff