Contractors conducted a deep clean at Eglinton Primary School by spraying a fine mist of disinfectant throughout the premises.
Several children who have been in direct prolonged contact with the teachers have been sent individual letters instructing them to self-isolate at home for 14 days.
A school statement said: “Following on from the 3 confirmed COVID cases in the last five days, we have made the decision to close the school to all year groups on Monday. This will enable us to use an anti-viral fog to sanitise the school before school re-opens as normal on Tuesday. Both classes in Reception will remain closed until further notice.”
The school is the fourth primary in south east London so far to register a positive case following Red Hill Primary School, Chislehurst, Trinity School, Lewisham, and Adamsrill Primary School in Sydenham.