The accident happened at approximately 6:00 pm in Jiangsu province, Xinhua news agency said, quoting a municipal government spokesman.
The school bus, belonging to the primary school of Zhanghoutun village, had been trying to avoid a vehicle when the accident happened, Xinhua said. The exact cause of the accident was still unknown.
On Sunday, China's cabinet published draft regulations aimed at improving school bus safety, after the deaths of 19 children in an overcrowded, nine-seater bus sparked a nationwide outcry in November.
The bus was carrying 64 passengers when it collided with a lorry in the northwestern province of Gansu, also killing two adults -- just weeks after another school bus accident left seven children dead.
Children are often crammed into buses for their journeys to school, especially in rural areas, due to lax enforcement of existing rules.