The alarm was raised yesterday at Saint Ignatius’ College Riverview and the school went into lockdown within hours.
This is expected to take some time as cleaners go through classrooms, halls, sporting facilities and outdoor areas.
The school aims to fully reopen next week in line with the resumption of classroom teaching in other NSW schools.
In a letter to parents, Saint Ignatius’ College Riverview said staff and students identified as close contacts of the student will be contacted and asked to self-isolate.
The school said the student who tested positive to the virus is not a boarder and has not had any contact with the school’s Regis Campus, which is reserved for years five and six.
“The school will be non-operational to the onsite attendance of staff and students while the school conducts contact tracing and is cleaned,” the letter reads.
“We anticipate this will be for no more than 48 hours.”
Boarding houses for senior students staying at the school will remain open.