Supt Chris Pearson said: “This is obviously an unsettling incident to occur on school grounds, and we are working closely with NUAST.
“A 15-year-old boy has sustained a stab injury and been sent to QMC for treatment. His injuries are currently believed to be serious.
“His family will be supported by specially trained officers while a thorough investigation is under way.
“We know this is likely to cause alarm and distress across our local community especially for parents and pupils in the area.
“What we know so far is that both victim and suspect are known to each other and there is no information to say this is linked to the national ‘School Wars’ social posts.
“We will be working closely with the school over the coming days to establish what has happened.”