Scores of angry parents protested outside a government-run school in New Delhi on Friday after a seven-year-old girl was allegedly raped by an electrician on its premises, police said.
The incident comes on the heels of sex-abuse scandals at two children's homes that have sparked widespread outrage.
The latest case came to light after the family noticed the child bleeding and lodged a police complaint on Thursday.
"A medical examination of the victim has been conducted. The results reveal a clear indication of sexual assault," Madhur Verma, a spokesman for Delhi Police, told AFP.
The 37-year-old electrician was arrested after being identified by the victim, Verma added.
Local media reports said the suspect, who had been hired by the school just a month ago, pulled the girl into a secluded water-pump room just as she was leaving to go home.
India has a grim record of sexual violence. Some 19,000 attacks on minors were reported in 2016, but activists say vast numbers are never brought to police attention due to the social stigma attached to sexual crimes.
In January an eight-year-old girl died after being kidnapped, drugged and gang-raped for days in northern Jammu and Kashmir.
The case led to the introduction of the death penalty for those convicted of raping girls younger than 12.