The girl, studying in Class 12 of Udayan Santiniketan School in Bezera, was found with serious injuries inside the school premises by the night guard last evening, a police official said.
The guard first took the girl to the local primary health centre but she was referred to the Guwahati Medical College Hospital today and died on the way.
Alleging that she was raped resulting in her death, local people gheraoed the Baihat Chariali police station demanding immediate arrest of the culprits and an inquiry into the incident.
Senior police and civil officials were camping in the area.