Parents whose children attend an elementary school in downtown Vancouver were given a notice over the weekend, warning them students in a specific cohort need to self-isolate due to a COVID-19 exposure.

A warning was first issued last week, after a possible COVID-19 exposure was reported in one class at Yaletown's Elsie Roy Elementary School from Sept. 22 to 24. At the time, parents were told they would hear from health authorities if their kids needed to self-isolate.

Then, on Oct. 3, parents got another letter from Vancouver Coastal Health saying all students and staff in that class must self-isolate for 14 days, but that isolation period was backdated to the last day they were in school during the three-day infection period. In other words, the class-wide quarantine will end this Thursday, even though parents weren't informed until Saturday.

"If the exposure already happened, and the kids were in school for a week, does it make sense to self-isolate now?" asked parent Ema Lale, whose twins are both in the class and are now quarantining at home.

Lale spoke to CTV News about the advisories after someone else posted an image of the letter on Twitter.

"They were in school, they were everywhere, going outside, just living our lives normally. So now we have to stay home. I can't work because I'm a piano teacher, so I work with children. For me it would be irresponsible to not share this information with my children, right?" Lale said.

She's immunocompromised, so she took her family to be tested after the first positive case in the twins' class was revealed. They all tested negative, but she said she wishes she knew what prompted the full classroom quarantine.

"We don't know what's changed, we don't know anything, we have no information, we are just in the dark," she said.

"There are so many cases of parents like me, who are immunocompromised, who will benefit from transparency."

Provincial health officer Dr. Bonnie Henry says there have been several full classes that have been ordered to self-isolate since the full return to class began, both in Vancouver Coastal and Fraser Health.

The reasons vary.

"It will depend on the age of the children, it will depend on how long somebody was in the infectious period when they were in the class and the activities that the class was doing," said Henry. It could also depend on whether the initial infection was in a student or a teacher.

VCH says it will not comment on specific school cases.

In a statement emailed to CTV News it said, "In a school setting, public health defines an exposure as a single person with a lab-confirmed COVID-19 infection who attended school and exposed others during the infectious period. An outbreak is declared at the discretion of the public health officer when exceptional measures are needed to control transmission. To date, Vancouver Coastal Health has not declared any outbreaks in schools."

"What we are seeing is a lack of transparency on reporting those situations," said B.C. Teachers Federation president Teri Mooring.

Coastal Health says protecting patient confidentiality is critical, something the teachers union insists can be done while still informing parents.

"There is a way to disclose information that doesn't disclose personal information about individuals, and we're still not seeing that," said Mooring.

If the full classroom quarantine is not because of an outbreak, Lale would like to know why it's necessary.

"This is not something that should be hush-hush at all," she said. "We are all just guessing. That is actually what creates a lot of anxiety."

Elbia Pinilla's daughter is also in the class.

"I am OK. I don't feel scared. Of course you have to follow the protocols and everything," said Pinilla. "If I freak out every time that's going to happen… This is the first one of many cases that is going to happen. I'm good."

After testing negative, Lale isn't worried about her health or the health of her twins. She just wishes health authorities would provide more information about why her family has to quarantine.

"It doesn't make sense, after 10 days, putting the kids in self-isolation," she said.