Two eight-year-old boys have died after a car crashed into a primary school classroom in Sydney, police have said.

The incident at Banksia Road Public School also left three girls in hospital with injuries.

Most of the other 19 children in the classroom were assessed at the scene by paramedics, authorities said.

The driver of the car, a 52-year-old woman, was taken to a police station. Authorities say they do not believe the crash was intentional.