A student has been arrested over the incident.
The injured student is thought to be in a serious condition and is receiving treatment in hospital.
Police were called out to the school in the Riverland region at 2.40pm local time.
The altercation involved two female students.
The school was briefly in lockdown, which was lifted once it was determined there was no risk to other students.
The crime scene remains cordoned off and is being scoured by police.
More details to come.
