Seven persons, including six school students, were killed on Saturday when a bus skidded off the road and rolled into a gorge in Himachal Pradesh's Sirmaur district, an official said.The victims, in the age group of 10 years, were going to Adarsh Vidya Niketan in Dadahu town when the accident occurred near Renukaji, a known Hindu shrine about 40 km from district headquarters Nahan and 150 km from the state capital.The dead included the bus driver.While seven injured students were admitted to the Y.S. Parmar Medical College in Nahan, five critically injured were referred to the PGI in Chandigarh.Deputy Commissioner Lalit Jain told IANS that the district administration provided a relief of Rs 20,000 each to the next of kin of the deceased and Rs 10,000 to the injured.Witnesses said the administration had a tough time extricating the victims from the badly-mangled bus.Prima facie the accident happened due to negligence of the bus driver, the police said.The state government in November banned plying of school buses older than 15 years after a school bus accident in Nurpur town in Kangra district that claimed 28 lives, including 24 students in the age group of nine to 12 years.The new rules include that drivers above 60 years of age will be debarred from driving and a driver must have a five-year experience of driving heavy vehicles. The driver will also have to undergo eye check-up every year.The new guidelines are applicable to all modes of transport, including buses and small vehicles like cabs and vans.