The 14-year-old girl, a student of Class 8, delivered the baby in the school hostel on Saturday night, Kandhamal District Welfare Officer (DWO) Charulata Mallick said.
The school is run by the SC (scheduled caste) and ST (scheduled tribe) development department of Odisha.
"The girl was raped eight months ago at her village. She couldn't reveal it out of fear and shame. The main accused has been detained," Kandhamal Superintendent of Police Prateek Singh told media persons.
Following the incident, as many as two matrons, one auxiliary nurse midwifery of the institute, two cook-cum-attendants and one warden were dismissed while three women Assistant Superintendents were suspended for dereliction of duty.
The district administration has recommended that the state government initiate action against the headmistress of the residential high school.
The SC and ST Development Minister Ramesh Majhi said the Kandhamal Collector has been asked to conduct a probe into the matter.
The Minister said appropriate action would be taken after the inquiry report is submitted.
Earlier, irate local residents staged a road blockade on National Highway-59, demanding action against the culprit. The blockade was withdrawn after police detained a youth, named as the accused in the case.