An ambulance was called to Holyrood RC Secondary School in the south side of the city at lunchtime after an "altercation" involving two 14-year-olds.
One boy was taken to hospital whilst the other was treated for minor injuries at the scene.
Police were called to the school on Brereton Street but it's understood the alleged attack happened outside the grounds of the school.
A Police Scotland spokeswoman said: "Around 1.20pm on Monday, police were called to a report of a disturbance in Boyd Street at Brereton Street in Govanhill.
"Two 14-year-old males were injured as a result of the incident and enquiries are ongoing to establish the exact circumstances.
"One of the injured males was taken to Glasgow Victoria Infirmary, and the other did not require hospital treatment.
"Police are following a positive line of enquiry."
In a statement Glasgow City Council said the head teacher would send a letter to all parents reassuring them the safety of children was of paramount concern.
It is Europe's largest school, with a roll of over 2,000 pupils, and over 130 teachers.