Katoomba High School will be closed on Friday after a member of the school community tested positive for coronavirus.

In an announcement late on Thursday night, the Blue Mountains school said staff and students should self-isolate while health authorities traced anyone who may have had contact with the infected person while he or she was contagious.

The school did not specify if the person who tested positive for COVID-19 was a student or staff member, only saying that it was a "member of the school community".

"To provide time for NSW Health to conduct their contact tracing process, the school will be non-operational Friday 13 March, 2020," the school said on its website and social media accounts just before midnight.