St Katherine's School has told two year groups of pupils to self-isolate after a confirmed coronavirus case.
The mixed 875-pupil secondary on Pill Road, Abbots Leigh, said Years 12 and 13 must stay home in a letter to parents on October 18.
It comes after the school told Year 10 pupils to self-isolate on October 11, following a previous confirmed case.
The latest letter reads: "We have been advised by Public Health England (PHE) that there has been a confirmed case of Covid-19 within the school.
"After a detailed investigation and following advice from PHE and national guidance, we are taking the following action:
"As you child is part of the Year 12 and 13 group bubble in which a positive case has been reported, they must stay at home and self-isolate until October 27 (this is 14 days after the reported contact).
"Therefore we plan to welcome Year 12 and 13 students back to school on Tuesday, November 3.
"Other members of your household can continue normal activities provided your child does not develop symptoms within the 14-day self-isolation period."
The letter said children should continue to follow their timetable and complete their work while home.
St Katherine's has been approached for comment.
More than 50 schools in the Bristol area have confirmed cases since the start of the academic year in September - the full list can be found here.
You should book a Covid-19 test if your child has at least one of the following:
A high temperature - This means if they feel hot to touch on the chest or back. You do not need to measure their temperature.
A new continuous cough - This means coughing a lot for more than an hour, or three or more coughing episodes in 24 hours. If your child usually has a cough, it may be worse than usual).
A loss or change to their sense of smell or taste - They've noticed they cannot smell or taste anything, or things smell or taste different to normal.
If your child does not have symptoms of coronavirus but has other cold-like symptoms, such as a runny nose, they do not need to be tested.
They and members of your household do not need to self-isolate.
In those circumstances, your child can attend school if fit to do so.
