The "majority" of pupils have returned to a Washington school after a coronavirus case.
Staff at Washington Academy found out about the case on Saturday.
However with a day, close-contacts had been tracked down and told to self-isolate.
It is the latest in a string of Covid-19 cases linked to schools around Sunderland and County Durham.
A dozen are either fully or partially closed after outbreaks. A full list can be viewed here.
However head teacher Sue Hamilton praised the "procedures and systems" in place at the Spout Lane school which enabled the contacts to be traced before pupils returned to lessons on Monday.
“We put clear support and advice in place ahead of the children returning to school, which has meant the right procedure has conducted swiftly, appropriately, and it has not impacted the school as a whole," she said.
"The majority of our school community can continue to come in – this is due to the fact that the right procedures and systems were in place right from the start to maintain social distancing guidelines. Through our thorough year group bubbling, it has ensured even few transmissions are possible.”
"Students have remained at a two-metre distance from students outside of their bubble during breaks, lunch time, and movements around the school building.
“Within 24 hours of the positive case being reported to the school on Saturday evening, we conducted a comprehensive review of any potential close contacts, who were informed to self-isolate for 14 days.
“It’s been a positive return to school and we’re proud to welcome our staff and students back following lockdown.
“It’s unfortunate that we are having to isolate some members of our school community over the next two-weeks as a precaution, but we look forward to getting them back in school as quickly as possible.”
