Three people are in hospital after a school bus travelling to a special developmental school rolled on a country road in north-west Victoria.

Emergency crews worked for more than an hour to free the bus driver after the crash involving a B-double carrying hay bales on Thursday morning.

A bus driver was trapped for more than an hour after a school bus rolled in country Victoria.

Three children and another adult were passengers on the bus at the time.

The bus driver was flown to a Melbourne hospital with serious injuries, while one child and the truck driver were taken to Horsham hospital.

The accident happened about 8.30am on Thursday, near the intersection of Stawell-Warracknabeal Road and Minyip-Dimboola Road in Minyip, about 51 kilometres north-east of Horsham.

The 22-seat school bus, travelling to Warracknabeal Special Developmental School, rolled onto its roof while the B-double hay trailer landed on its side.

Three people were taken to hospital.

The school caters for students with disabilities aged 5–18 years from Warracknabeal and surrounding areas, according to its website.

The female bus driver was trapped for more than an hour before she was freed by 9.45am, the Country Fire Authority said. Police said she sustained serious injuries in the crash.

A specialist Ambulance Victoria helicopter crew and six advanced life support paramedic crews arrived at the crash site about 8.50am.

“Following emergency on-site care by our crews, two people have been transported by road ambulance to Horsham hospital and one person has been airlifted to The Alfred,” an Ambulance Victoria spokeswoman said.

The bus driver was in a stable condition in hospital on Thursday afternoon.