By Agence France-Presse
The 39-year-old assailant used a kitchen knife to slashed students while they were returning to the classroom after morning exercises, said the Banan district public security bureau in Chongqing city on its official social media account.
Images and video footage posted by local media online show children in blood-soaked clothes, some with knife wounds on their face.
After police rushed to the scene, children were evacuated for medical treatment. The woman who carried out the attack is currently in police custody and an investigation is ongoing.
The attack took place at about 9:30 am (0130 GMT) local time, according to the department.
Knife attacks targeting schoolchildren are not uncommon in China, which has seen a slew of deadly incidents over the past few years.
In April, a 28-year-old man killed nine middle school students as they were returning home in one of the country's deadliest knife attacks in recent years. The killer, who said he had been bullied when he attended the school, was executed in September.
In January 2017, a man armed with a kitchen knife stabbed and wounded 11 children at a kindergarten in southern Guangxi Zhuang autonomous region.
Such events have forced authorities to increase security around schools and led to calls for more research into the root causes of such acts.
Violent crime has been on the rise in China in recent decades as the nation's economy has boomed and the gap between rich and poor has widened rapidly.
Studies have also described a rise in the prevalence of mental disorders, some of them linked to stress as the pace of life becomes faster and support systems wither.