A school has closed after eight members of teaching staff tested positive for Covid-19.
Samuel Ward Academy in Haverhill, Suffolk, said 90 students – three classes – had been told to self-isolate for 14 days.
Unity Schools Partnership, Suffolk County Council and Public Health England said the closure was a “precautionary measure” and the school would undergo a deep clean.
It is hoped it will reopen on Tuesday.
The school’s staff training days were held on Tuesday and Wednesday last week, with pupils making a phased return from Thursday.
All year groups were due to be at school on Monday.
Head teacher Andy Hunter said it was a “huge disappointment” but the safety of pupils and staff was his “biggest priority”.
He said: “I will be looking closely at the systems we put in place to try to understand how the transmission occurred and to make sure we do everything possible to limit the chances of the same thing happening again.”
Mr Hunter said the secondary school would be looking at a number of measures, including whether children should wear masks in public places and if staff meetings ought to be held virtually.
He said anyone who has been in close contact with infected staff had been contacted and told to self-isolate for 14 days – including 90 pupils.
Stuart Keeble, director of public health at Suffolk County Council, said the news “may worry parents across Suffolk” but it was “important to remember that the risk of children contracting Covid-19 is still very small”.
Dr David Edwards, from Public Health England East, said the closure would enable contact tracing to be completed so anyone needing to self-isolate was informed before returning to school.
Old Buckenham High School in Norfolk has also been closed after a member of staff tested positive for coronavirus.
It said there would be a deep clean and it would reopen as soon as possible.