Health officials are investigating the situation at Douglas Ewart High School in Newton Stewart and parents have been informed.
Interim public health director Valerie White today said the NHS is working closely with the council on the situation and reassured parents that it is being closely monitored.
She said: “As is the case in schools across Dumfries and Galloway, arrangements are in place at Douglas Ewart to limit risk of transmission. Risk assessment work has been undertaken on this basis and the families of potential close contacts have already been notified and provided with guidance.”
And director of education Gillian Brydson added: “The safety of pupils and staff within our schools is out utmost priority.
“We have a very integrated approach to our Covid 19 response, working in partnership with NHS Dumfries and Galloway. The Test and Protect system within our region has proved very robust and effective and will be employed in this situation.”
She stressed that pupils of the school can continue to attend unless they have been contacted by Test and Protect and as long as they and their household are all well.