GUELPH -- A French Catholic elementary school in Guelph has confirmed 18 COVID-19 cases among students and staff since the school year began.

According to the province's school case dashboard, 17 of the infections at École élémentaire Catholique Saint-René-Goupil are among students and one is in a staff member.

As of Wednesday, that's the most school COVID-19 cases at any school in the province, figures from the dashboard show.

"It is a little alarming to see the number of cases, especially in such a short period of school being on," said parent Jessica Cossette.

Wellington-Dufferin-Guelph Public Health has declared a school-wide COVID-19 outbreak at the small French immersion school.

With 244 students at the school, that means about seven per cent of students have tested positive for the virus.

Health officials maintain spread is not happening in the classroom but instead at home.

"At this point WDGPH maintains that transmission has not occurred at the school but has established that it has happened at home," Mikale-Andrée Joly, a spokesperson for the school board, Conseil scolaire catholique MonAvenir, said in an emailed statement. "Siblings of students from the first class closed are catching COVID-19 at home. Once these siblings are reported sick, WDGPH asks that their classes be closed as well."

The school's website shows five cohorts have been dismissed due to COVID-19 cases.

"The school and Board administration continue to work closely with Wellington-Dufferin-Guelph Public Health (WDGPH) in order to understand the reasons for which there continues to be cases reported throughout other classes, even when the class where the first case originated has been closed since September 13th," Joly said.

"The issue is there's classrooms (with) multiple cases, and when it's multiple cases, the issue has nothing to do with the household it has to do with school transmission," said Ryan Imgrund, a biostatistician who tracks COVID-19 cases in the province.

Despite the high number of cases and the school-wide outbreak, the Saint-René-Goupil remains open.

"The goal is to work with the school and families to keep the school open," Chuck Ferguson, a spokesperson for WDG public health, said in an emailed statement.

He said the health unit is working with families on what to do if a child is considered to have had a high-risk exposure to someone with COVID-19.

"If that child is unvaccinated any unvaccinated household member needs to stay home from school, childcare, and any non-essential activities," Ferguson said. "Because of how transmissible the Delta variant is WDG Public Health is applying this protocol to all schools."

Earlier this week, the health unit issued new protocols for unvaccinated household members of high-risk COVID-19 contacts. All unvaccinated members of a close contact's household must now also isolate until cleared by public health.

Public health and the school board are reminding parents to monitor children for COVID-19 symptoms and not send them to school if they are unwell.