She said her grandson revealed in his diary that a person with stronger self-esteem may have thought of suicide after being treated this way.
In a circular, Shaanxi provincial educational department on Saturday said though the slapping was an isolated case, it was very bad and lessons shall be learnt.
The educational authorities said it plans an overhaul to stop teachers' malpractices such as brutality, insults and discrimination towards students.
Luo apologized and offered a financial remedy to the student's family. The school also covered part of the medical expanses.
The student has now returned to school after treatment, the authorities said.
The centuries-old child-raising philosophy "sticks make a great man" has deep roots in Chinese society. Calls to end strict teaching and parenting methods that sometimes cross the line have only become popular in recent years.