The Health Protection Team at NHS Highland is working with Highland Council Education Service following the confirmation of the latest case involving a child at Helmsdale Primary.
The child did not catch the infection at school and remains well.
A leaflet providing further information has been given to all parents and staff.
A health board spokeswoman said: "NHS Highland are continuing to investigate this case and will provide further advice to parents and staff after school reopens following the midterm break holiday on Monday."
She added: "For TB to spread the affected person must be infectious and also to have had prolonged, close contact with others.
"Such contact is usually only found in the home. It is unlikely there has been any spread from a school."