A third of kids and seven out of 50 teachers at Kirkcudbright Academy are thought to have caught the deadly bug this week.
Health officials in Dumfries and Galloway have drawn up emergency plans to prevent the outbreak getting worse. Other schools across the region are being warned to expect further cases.
Officials said those affected have mild symptoms and tests are being done to establish if they have swine flu.
They are sure the virus has been contained and said there is no need to close the school.
Consultant Dr David Breen said last night: "I would seek to reassure the public that it appears to be following a fairly typical and milder development of the symptoms and none of those affected currently require hospital intervention.
"The school remains open and is operating as normally as possible under the circumstances.
"Public health staff are monitoring the situation closely. We are confident that all appropriate measures have been taken by GP colleagues, Academy and education department staff and by NHS public health teams.
"We will continue to monitor closely the situation and take appropriate actions where necessary.
"As yet, it is not possible to confirm the outbreak as H1N1."
Source: The Sun Online, 6th November 2009