An entire year was sent home from school until October after two students tested positive for Covid-19.
St Hilda's High School, near Sefton Park, has sent a letter to parents and carers of the school to make them aware of the situation.
Two students in year 11 tested positive for the virus earlier in the week meaning the entire GCSE year were sent home as precaution.
Headteacher Mrs Jo Code told guardians that the whole group would now need to self-isolate for 14 days.
In the letter, she said: "As I wrote earlier, we have two confirmed cases of Covid-19 in Year 11.
"I sent Year 11 home today once I became aware of the positive test results which were reported to us early this morning.
"At this stage it was a precautionary measure to allow me to investigate.
"After speaking to both students and their parents I now feel the need to self-isolate the whole year group to ensure that we reduce the further spread of Covid-19 to others in our community."
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A number of parents were also told that the affected students had named some pupils as a close or direct contact.
Mrs Code added: "Both students have not been in since Tuesday. so we are able to count Wednesday as the first day of self-isolation.
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"This means that, providing your son or anyone in the household does not test positive or have Covid-19 symptoms in the meantime, they can return to school on Wednesday 7th October.
"If your son does have Covid-19 test and it is negative, it does not mean that they can return to school earlier than the date above."
Guardians were then reminded that other members of the household did not have to isolate if the child does not develop symptoms within the 14 day isolation period.
