image captionThe head teacher said the building had been successfully deep-cleaned
Some 90 pupils at Samuel Ward Academy in Haverhill, Suffolk, were told to self-isolate for 14 days as a result.
Head teacher Andy Hunter said half of the school had reopened after cleaning, but it would be another 12 days until all pupils could go back.
Mr Hunter said all staff and students must wear masks in “public areas” of the school such as corridors.
image captionPublic Health England gave the school the “all clear to open”, head teacher Andy Hunter said
“Due to the significant number of staff self-isolating, both because of positive tests and for precautionary measures, we will be operating a rota system among year groups for the rest of this week and next week,” Mr Hunter said.
The academy aims to reopen fully on Monday, 21 September.
Mr Hunter said new procedures had been put in place which go “way beyond the government guidance” regarding social distancing between staff and between staff and pupils.
Staff meetings consisting of more than two people would be held virtually and everyone should wear face coverings in “public places” such as corridors, stairwells, toilets and washrooms, changing rooms and canteen queues.
Meanwhile, Old Buckenham High school in south Norfolk, which was also closed on Monday after a member of staff tested positive for coronavirus, reopened on Tuesday following a deep-clean.
A number of staff were self-isolating for two weeks, but the head teacher, who was himself isolating, said the school could reopen safely.