TORONTO -- Ontario is reporting 21 new COVID-19 cases in schools around the province, including at least five among students.

The first COVID-19 case in a Windsor-Essex school was reported on Tuesday, at Stella Maris Catholic Elementary School in Amherstburg.

The new cases -- which also include four staff members and 12 people who aren't identified -- bring the total number of schools with a reported case to 51 out of the province's 4,828.

That number includes one high school in eastern Ontario that's been ordered to close after three staff members tested positive.

The Renfrew County District School Board posted a notice on social media Wednesday saying the local public health unit had ordered the immediate closure of Fellowes High School in Pembroke, Ont.

The notice says the third case was detected on Wednesday and was linked to two previously announced cases, all among staff members at the school northwest of Ottawa.

Meanwhile, Premier Doug Ford is set to announce today the number of people permitted at social gatherings in three regions of Ontario will be lowered.

This report by The Canadian Press was first published Sept. 17, 2020. With a file by CTV Windsor.