Two new individual coronavirus cases have been identified at schools in Johnstone and Dundee, the First Minister has confirmed.
Contact tracing is now being carried out.
The news comes after two school pupils from Perth and Kinross and a pupil at Todholm Primary in Paisley also tested positive for Covid-19 this week.
Covid outbreaks at schools have become a concern since pupils returned to class earlier this month.
In Glasgow and Lanarkshire, health officials are investigating a number of coronavirus cases linked to house parties.
A total of 14 positive cases were identified – some of whom are pupils at Bannerman High School in Baillieston.
NHS Lanarkshire is also carrying out a community-wide investigation after a spike in Covid-19 cases among pupils at several high schools in the area.