Rainford High School in St. Helens closed its doors to all students on Monday, September 28, after nearly 40 students tested positive for the virus.
A school in Merseyside had to close after an outbreak of coronavirus cases among “asymptomatic” students.
The school conducted its own mass testing of 1,100 students.
He said the school was suffering from transmission “from the community across all grades”.
In a letter sent to parents’ homes on Monday, principal Ian Young said that some students tested positive for the virus even though they did not show symptoms.
The cases were revealed after the school conducted its own mass testing of 1,100 people under the guidance of Public Health England and St Helens Test and Trace.
In the letter that the Echo saw, Mr Young said: “As you know, under the guidance of Public Health England and with the support of the St Helens Test and Trace team, 1,100 members of the school community were tested for Covid 19 on Thursday and Friday last week.
To prevent further spread of the virus, the school will remain closed until Monday 12 October.
“This brings the total number of live cases to just under 40.”
“Unfortunately, a significant minority of the students tested positive for the corona virus, although they were asymptomatic.
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He continued, “There is evidence that Rainford High is suffering from community-based schooling transfer across all grades.
“Because of the risk this poses to the school and the wider community, it has been recommended that Rainford High be closed with immediate effect and reopened on Monday 12 October, when we hope to resume school with a full return to school.
He said the school’s “proactive and proportionate approach” with Public Health England had led to the unprecedented program of mass testing.
Mr Young went on to say that the school had followed all national guidelines regarding corona viruses and that risk assessments and procedures were regularly reviewed.
Later today, a joint letter from the school, Public Health England and St Helens Council will be sent to parents and carers with more information on distance learning.