The school board says Saint Andre Bessette Catholic Secondary School, St. Kateri Catholic Elementary School and Mother Teresa Catholic Secondary School each have a case of COVID-19.
All three schools will remain open and school buses will continue to operate, the LDCSB said.
They say parents, guardians and staff at all three schools have been notified while the MLHU works to track down close contacts.
This marks at least the 11th, 12th and 13th COVID-19 cases to be reported at local schools in London and Middlesex.
The latest COVID-19 case to be reported at a school in the region was on Oct. 16 at Banting Secondary School.