KITCHENER -- A staff member at Centennial Public School in Waterloo who tested positive for COVID-19 went to work while they were infectious and waiting for their test results.

Waterloo Region District School Board spokesperson Alana Russell confirmed the information to CTV News Kitchener on Wednesday.

"Public health has determined that this individual was at the school for a period of time while symptomatic or during the infectious period and so as a result their last day of school was Nov. 17 and they've been directed by public health to self-isolate until further notice," she said.

The school board's website showed that the positive result was reported on Tuesday. It can take up to a few days to receive testing results, Region of Waterloo Public Health's website said.

"This is a unique situation where we did have a staff member that was attending school while awaiting test results because we know that our staff do an excellent job of adhering to our health and safety protocols at the schools, not just for themselves but for their students and their classrooms and so we will be investigating the circumstances here and determining how this occurred," Russell said.

She called the situation "unfortunate" and "disappointing" that went against the protocols the school board has in place and urged any staff members who are feeling unwell to stay home.

"I was very shocked," one parent told CTV News Kitchener.

The school board said this was an isolated incident that doesn't reflect the efforts to keep staff and students safe during the pandemic.

"This is an unfortunate situation which runs in direct contraventions to the strict health and safety protocols that we have at our schools," Russell said.

During a media briefing on Wednesday, Premier Doug Ford called the news "unacceptable."

"I can't believe someone would do it still after just preaching up here non-stop. Do not go into work, do not go to school, do not go to hospital, do not go to long-term care," he said.

High-risk contacts, including some other staff members at the school, have been notified to self-isolate. Six cohorts from the 470-person middle school have been dismissed and will also be self-isolating until Dec. 2, she said.

The Ministry of Labour tells CTV News that they conducted a visit to the school on Friday. No orders were issued as the investigation remains ongoing.

The staff member was the first case of COVID-19 that was confirmed at Centennial Public School, the WRDSB's website shows. There have been 21 cases in WRDSB schools through November so far. Forty-six students and staff members have tested positive in the public board's schools since the start of the school year.

The Catholic school board has reported 15 cases in its schools this month, and a total of 28 cases since the school year began.

CTV Kitchener is tracking every case of COVID-19 in publicly funded schools. Keep up to date with our interactive map.

With files from CTV News Kitchener's Nicole Lampa

Correction:

This article has been updated for clarity. The Waterloo Region District School Board originally stated that staff member went to school while symptomatic.

The WRDSB has since clarified that they couldn't confirm whether or not the person was symptomatic, but that public health officials had said the person was at work while infectious and awaiting their test results.