Education chiefs at Old Swinford Hospital school said Year 7 students should isolate before returning back to the school on November 30.
It comes as four members of staff have tested positive for Covid-19 – with another eight told to self-isolate through the NHS Test and Trace app.
Headmaster Paul Kilbride, in a letter sent to parents, said discussions had been held with Public Health England and the council.
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He said: "Having spoken today with the local authority, the public health and wellbeing directorate and having discussed the matter with PHE, it is clear that the local, regional and national context has changed quite radically over the past few days.
"In our own authority, seven schools are currently closed and most have groups self-isolating. Sending pupils away to self-isolate is never an easy decision, but in the interests of the safety of the community and its ability to continue to function effectively it is one I reluctantly take."
Day pupils and flexi-boarding pupils will now need to remain at home – unless they need to opt into boarding for the whole of the 14 day period and stay in the house and residents.
All Year 7 pupils – in and out of Prospect House – will be able to follow their lessons via Satchel One and Teams, education chiefs have said.