Emergency services were called to Glenwood High School in western Sydney about 1pm on Thursday.

Police found the 16-year-old with two "significant' stab wounds to his stomach.

They arrested a 14-year-old school boy, who Acting Superintendent Jason Pietruszka says will be charged.

A/Supt Petruszka said early inquiries suggested a "typical, everyday schoolyard argument" had made its way onto social media and ultimately led to Thursday's violent incident.

"It is incredibly stupid to engage in this type of behaviour," he told reporters.

While the victim's injuries could have been fatal, they're not considered life-threatening, the officer said.

The boy is being treated at Westmead Hospital, where he was taken by ambulance.

A/Supt Petruszka pledged that police would take schoolyard violence very seriously.

"It's not worth your future," he said. "Do not do it."

Australian Associated Press