Pupils at Elgin Academy are self-isolating after a Covid case was confirmed there.
The school has written to all parents to inform them about the case.
Pupils only returned full-time to the secondary school on Monday following the lockdown and Easter holidays.
Any student that came into close contact with the positive Covid case has been asked to self-isolate.
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Elgin Academy will remain open in the meantime.
The school has worked closely with NHS Grampian’s Health Protection Team to identify which pupils need to self-isolate.
They looked at the movement of the pupil throughout the school building, on school transport as well as seating plans and classroom layouts.
A spokeswoman for Moray Council said: “Our main concern first and foremost is for the wellbeing and good health of those concerned and we wish them a speedy recovery and hope their family stay well.
“We’re in contact with NHS Grampian’s public health team, who advised on the cohort of pupils and a teacher to be informed they should enter self-isolation, and will continue to advise us on matters of public health. These pupils have also been provided with information on how to access their learning from home.
“All Moray schools receive an enhanced clean daily as standard now in line with Public Health advice, including daytime sanitation, and this allows the rest of the school to continue as normal.
“School buses, which are considered an extension of the school estate, are also cleaned after each run so we’re satisfied that Covid-19 safety measures continue to be met.
“We ask anyone contacted through the Test and Protect process to follow the guidance given, and any health-related questions are directed to the NHS.
“Families will continue to be kept informed by the school on any further action to be taken.”