A teenage girl has been stabbed during a brawl outside a western Sydney public school, with police now searching for several people who fled the scene.

Emergency services were called to Lancaster St, Blacktown, about 2.30pm on Friday after reports of a fight involving around half a dozen people.

WATCH THE VIDEO ABOVE: Teenage girl stabbed outside school

Know the news with the 7NEWS app: Download today

Paramedics treated a 17‑year‑old girl for multiple stab wounds before she was taken to Westmead Hospital in a stable condition.

Police allege the teenager ran onto school grounds to seek help after being stabbed. The girl has no affiliation with the school.

Officers have been told a car possibly linked to the brawl was last seen driving north along Lancaster Street.

All other people involved had fled before officers arrived.

Police at the scene. Credit: 7NEWS

A crime scene has been established and detectives from Blacktown Police Area Command have launched an investigation.

Anyone with information is urged to contact police.