The junior campus at Caroline Chisholm School is closed for deep cleaning on Wednesday, after a COVID exposure last Friday.
A person attended the junior campus while unknowingly infectious on Friday October 15, between 8.40am and 12.30pm.
"ACT Health is conducting a risk assessment and contact tracing to determine which people on the school campus on this day are classified as having had an exposure and to provide further instruction," school Principal Jennifer Howard wrote in an update to parents on Tuesday night.
Primary students haven't yet begun their return to on-campus learning, with preschool to year 2 as well as year 6 among the groups due back next Monday.
Children who can't learn from home have still been allowed to attend schools, before they return in full.

Anyone who attended the school campus at the identified times should stay home awaiting further advice from ACT Health following the risk assessment. That advice is expected to be issued later on Wednesday.
Parents who dropped their children at the campus but did not enter the premises are not considered to have attended the school and don't need to stay home.