Moreton School posted on its Facebook page saying the "small number" of children who have been in direct prolonged contact with the staff member will be staying at home for 14 days.
A letter sent to parents this week says: "We have been advised by Public Health England that there has been a confirmed case of Covid-19 within the school.
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"We know that you may find this concerning but are continuing to monitor the situation and are working closely with Public Health England. This letter is to inform you of the current situation and provide advice on how to support your child. Please be reassured that for most people, coronavirus (Covid-19) will be a mild illness.
"The small number of children who have been in direct prolonged contact with the confirmed case have received an individual letter and will be staying at home for 14 days.
"No other students will need to self-isolate as they have not been in prolonged contact with the member of staff affected.
"The school remains open and your child should continue to attend if they remain well."