The Mary Webb School & Science College in Pontesbury has also sent home its Year 10 students due to two of the pupils who tested positive for coronavirus being in that year group.
The school said it is working with Public Health England and Shropshire Council after the three cases were confirmed and they have followed local guidelines and protection advice, including isolating all possible school contacts.
As a precaution, 31 pupils have been asked to self-isolate for 14 days and the school remains open for all years apart from Year 10.
No members of staff were identified as close contacts and the isolating pupils will be taught at home, the school said.
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The school has informed parents, carers and staff of the situation and measures continue to be taken to make the school Covid-19 safe.
Rachel Robinson, Shropshire’s Director of Public Health said: “We want to reassure students and parents/carers that the risk of infection remains low. The school has acted responsibly and taken all the necessary precautions to limit the spread of the virus, which in this case requires a number of pupils to self-isolate
“Anyone from the school community and their families who is symptomatic will be offered immediate testing. Contact tracing is underway and if anyone is identified as a contact of a confirmed case of Covid-19, a contact advisor from Test and Trace will be in touch with appropriate advice.
Peter Lowe-Werrell, Headteacher The Mary Webb School & Science College said: “We have been made aware that three members of our school community have recently tested positive for Covid-19. In line with national guidance, we have asked 31 pupils to self-isolate.
"As two pupils were in the same year group, Year 10, and were not in the same classes or friendship group, we decided to temporarily close Year 10. All students self-isolating and the remainder of Year 10 will return to school again on Tuesday, December 1.
“All affected students will continue to be taught remotely whilst self-isolating. The school remains open for all other year groups.
“I realise this may cause some inconvenience for parents and carers, but these measures are being taking in the best interests of our pupils and staff.”
Mrs Robinson reminded people to stay at home as much as possible, and limit contact with other people outside individual households.