Head teacher at Hymers College Mr David Elstone said the pupil who contracted swine flu is making a full recovery.
"It is business as normal at the school. We have fewer absences today than we would probably have on a normal day in July."
Mr Elstone said the name of the boy would not be released by the school.
But it is understood to be Matthew Fitzpatric
k, who is a year 10 pupil at the fee-paying Hymers College.
Mr Elstone confirmed: "One of our children has tested positive for swine flu. The child has received the appropriate treatment and is recovering well.
"On receiving the news the school has acted promptly and, working alongside the Health Protection Agency (HPA), has issued a detailed letter to all parents and staff, explaining the circumstances and outlining the symptoms.
"Public health experts at the HPA and the local NHS have advised us that any risk to the rest of the school community is low.
"At the present time we have been advised that the school should remain open but we are continuing to monitor the situation closely with the relevant health organisations and will keep parents and carers informed of any changes.
"Although the risk is low, the HPA and local NHS will be offering anti-viral medication to close contacts of the confirmed case as a precautionary measure. We are in regular contact with the HPA and the local NHS to ensure that school life continues as normal and we have contacted parents and carers to explain the situation."
