An entire school year group have reportedly been forced to self-isolate after one pupil tested positive for coronavirus.
Staff and students at Liverpool College were told on Sunday that the Year 11 'bubble' had been affected.
Liverpool City Council confirmed it was one of eight schools affected by Covid-19 just days after pupils began returning to school last week.
At least 120 pupils and 21 members of staff across the schools are self-isolating as a result- just days after they had finally returned to the classroom after months of remote learning.
Liverpool College, a mixed day and boarding school for pupils aged 4 to 19, had only just reopened on Thursday.
At least 145 pupils in Year 11 at Liverpool College believed to have been affected, along with some staff - although the exact number is yet to be confirmed.
The academy school has been cleaned, and the rest of its classrooms remain open, its principal told families in an email.
It confirmed to Mirror Online that the Year 11 bubble are self-isolating.
Principal Hans van Mourik Broekman said in a statement: "I can confirm that a pupil has tested positive for Covid-19.
"As a result, and in line with public health advice, pupils in the 'bubble' affected are not attending school and are self-isolating at home for 14 days. Their teaching will continue via online platforms."
Liverpool City Council confirmed seven other schools in the major city are also affected by coronavirus cases.
A total of four members of staff and two pupils across those schools have tested positive for coronavirus, its spokesman said.
Four primary schools, three secondary schools and one special school are affected, with a total of 120 pupils and 21 staff self-isolating, a council spokesman confirmed.
Mr van Mourik Broekman wrote in an email to Liverpool College parents on September 6: "We have been advised that there is a confirmed case of COVID-19 within the Secondary Phase in Year 11.
"I would like to take time to reassure you that we have taken all necessary actions since receiving this information to keep all children at our school as safe as possible
"The children and staff in the bubble affected have been notified and are now self-isolating for 14 days. Their learning will continue via remote learning platforms. School remains open as usual for all other pupils.
"The school has been cleaned appropriately."
Millions of pupils have now returned to the classroom after nearly six months out of the classroom.
As of Sunday, at least 62 UK schools had already been hit by Covid-19 positive tests - forcing many to send pupils and teachers home again.
