A vomiting bug has spread through Larchfield Primary and Nursery School.
Eighty children were sent home last week in a bid to stop the spread of the illness.
Deputy head Tim Dunning said about 30 children had fallen ill on Wednesday afternoon with sickness and diarrhoea.
They were all sent home and a further 50 pupils were also told to stay at home as a precaution.
He said the school was 'open for business as usual' and added: "We are working with a public health officer and the health and safety of the children is paramount."
It is not known if the illness is contagious and the cause is still being investigated.
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