A police spokeswoman said: “Following reports of an incident at Cults Academy at approximately 1.30pm today, one male pupil has been taken by ambulance to Aberdeen Royal Infirmary with serious injuries.
“A further male has been detained and is currently assisting officers with their enquiries.
“Enquiries into the circumstances of the incident are ongoing and officers will remain at the scene for the time being. Next of kin are aware.
A police officer stands guard outside the school
A number of concerned parents have arrived at the school but are not being allowed to enter the building.
An Aberdeen City Council spokesperson said: “We are aware of a serious incident at Cults Academy today. Police are on site.
“Due to the nature of this incident we will not be issuing further comment.”
Police at the scene at Cults Academy
One male taken to hospital and another detained by police following serious incident at Cults Academy