The head of a Cardiff secondary hit by swine flu said the school's detailed preparations had helped keep parents alert to a potential outbreak.
As TES Cymru went to press, two Whitchurch High pupils had been diagnosed with the virus and there were a further six suspected cases.
The school - the largest in Wales, with around 2,500 pupils - was kept open on the advice of the council.
Huw Jones-Williams, the head, said the school had taken the swine flu threat seriously and drawn up a comprehensive policy in May.
He congratulated parents for following the advice when their children started showing symptoms.
Parents are being kept updated through the school's website.
Mr Jones-Williams told TES Cymru: "We have taken this very seriously. Our concern is for the pupils, that they make a swift recovery. We will continue to take professional advice and keep staff, pupils and parents informed."