The Waterloo Catholic District School Board says it's pushing the start of virtual school to Sept. 17.

The school boards virtual school, called St Isidore, has been delayed to complete scheduling and staffing, the WCDSB said in an update posted on its website.

The Catholic school board welcomed the first of its students back on Tuesday morning. Students will return in a staggered schedule over the next few weeks.

Elementary students interested in switching between in-person or virtual learning will be able to switch at Thanksgiving, the school board said. Secondary students can change after the end of their first semester in early November. The school board said it will have more information about informing officials about changes soon.

"We know some of you wanted to switch now, but we did have to close that window, as it is critical to the exercise of contact-tracing and forming cohorts, to account for each and every child," the school board's update said.

The schedule change means both elementary and secondary students will start virtual school though St Isidore on Sept. 17.