The principal and a teacher of an English medium school in the old city area allegedly taped the mouth of a Class 9 student for talking in class and made her remain standing for four hours on Wednesday.
Syeda Sada Fathima, 14, has been traumatised by the punishment, which she said included a beating.
Gagged with cellophane tape, the Sam British School student could not eat or drink during the punishment, which lasted from 10.30am to 2.30pm, and returned home crying with an untouched tiffin box.
"The principal, Afroz Mazar, walked into the classroom when I was talking to other students. She ordered class teacher Sajida to put adhesive tape on my mouth. I was ordered to remain standing," Fathima said on Thursday.
The private school's management denied Fathima was punished. "We are a responsible school and do not believe in corporal punishment. The girl was only chided, never punished," Mazhar Ali, the school's co-owner and husband of the principal, said.
Officials from Dabeerpura police station visited the school in Noor Khan Bazar after registering a case on the complaint of Fathima's father, Syed Mujtaba Hussain, against the principal and the teacher.
"After my daughter told me what had happened, I shifted her to a hospital and went to the school. But the principal said she had done nothing wrong," said Hussain, a reporter with a local television channel.
He said seven other students had told police they had faced similar punishment.
Police are yet to make any arrests. The Andhra Pradesh government has ordered the district education officer to conduct a probe into the incident.
Fathima's parents are planning to move the state human rights commission.