A total of 22 coronavirus cases, most of them adult staff, have now been linked to a school in Dundee.
Kingspark School was closed last Wednesday as pupils and staff were asked to self-isolate for 14 days.
NHS Tayside said in an update on Sunday that 17 staff, two pupils and three community contacts had tested positive.
Two other school sites in Dundee have also been identified as result of contact tracing connected to the Kingspark outbreak.
A primary two class at St Peter and Paul’s School has been asked to self-isolate until 2 September after an individual tested positive.
Children who attended the Happy Times out-of-school club at Downfield Primary School are also being asked to self-isolate until the same date following a positive test result.
Elsewhere, two classes at High Blantyre Primary School in South Lanarkshire are self-isolating after two pupils and a staff member tested positive.
NHS Lanarkshire said there was no evidence to suggest transmission within the school and the school will remain open.
Kingspark School in Dundee, which has about 185 pupils aged between five and 18 who have additional support needs, was closed on Wednesday evening to allow deep cleaning to be carried out.
The decision was taken to shut it for two weeks because of the complex health conditions of the pupils.
Pupils and anyone who lives with them who cannot maintain physical distancing have been asked to self-isolate for 14 days.
Dr Ellie Hothersall, consultant in public health medicine at NHS Tayside, said: “Since the identification of positive cases at Kingspark, a detailed contact tracing programme has been under way and these linked cases are being identified because of those concerted efforts of Test and Protect.
“We must do everything we can to protect all of our communities against Covid-19 and that is why we have issued the guidance to self-isolate. By taking this action we are containing any further spread of infection.
“We know that this may cause anxiety to some parents and children but we must do everything we can to ensure we keep people safe.”
Paul Clancy, Dundee City Council’s executive director of Children and Families Services, said: “I would like to reassure families that this action is being taken to keep everyone safe.
“This is our paramount concern and we cannot be complacent.”