Parents and carers of South Shore Academy pupils were contacted on Tuesday, November 30, and informed of the three day-long emergency closure, which started the next day.
A letter from head teacher Rebecca Warhurst read: "Due to a highly infectious sickness and diarrhoea outbreak, which is likely to be norovirus, Public Health have advised to close the school with immediate effect in order to break the infection cycle. School will be closed tomorrow, Wednesday December 1 until Monday December 6. All students must return to school if they have been symptom-free for at least 48 hours on Monday... as normal."
She added: "Public Health have advised that although this outbreak is likely to be norovirus, as vomiting can be a symptom of Covid, that all students irrespective of having symptoms or not must conduct a lateral flow test, and for this to be negative, before returning to school on Monday.
"All students who have recently had physical sickness and/or diarrhoea must not return to school until they have been clear of all symptoms for 48 hours and must have received a negative PCR test result."
Online classes were set up throughout the closure. Families of children without access to online learning were invited to pick up work from the school on Wednesday between 8am and 1pm.
Children entitled to free school meals were sent electronic vouchers, as in previous Covid-19 lockdowns.
A Blackpool Council spokesman said: "There was an outbreak at South Shore Academy last week, the school moved to online learning for a short period of time to enable further infection control measures to be put in place. The school has since re-opened.
"Unfortunately winter viruses are common and we would urge parents to keep children at home if they are unwell. Children should be symptom free for 48 hours before returning back to school which helps to contain the spread of all winter viruses.
"Covid-19 symptoms are similar to other winter viruses, we would urge people if they have symptoms and are at all unsure then to get a PCR test."
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