A school bus carrying more than 40 teenage students has crashed in Sydney's west, leaving the driver in a critical condition and several students injured.
Emergency crews were called to Erskine Park Road at Erskine Park about 1pm today after the bus veered off the road and crashed into a tree.
Police said the bus was carrying a teacher and 41 students in years 11 and 12.
READ MORE: Con-woman Melissa Caddick's victims share 'small pot' last cash
Paramedics treated a number of students at the scene, with five teenagers aged between 16 and 18 taken to hospital for treatment.
One is believed to have suffered fractures.
A NSW Ambulance spokesperson said the driver, a man believed to be in his 50s, is suspected of having suffered a medical episode before the crash.
READ MORE: Australia is one of the richest countries in the world. But household debt is making us feel 'poor'
He became trapped inside the vehicle for a short time before emergency crews freed him from the wreckage.
The driver was taken to Westmead Hospital in a critical condition.
NEVER MISS A STORY: Get your breaking news and exclusive stories first by following us across all platforms.
- Download the 9NEWS App here via Apple and Google Play
- Make 9News your preferred source on Google by ticking this box here
- Sign up to our breaking newsletter here