The 15-year-old student was allegedly beaten with stick by his teacher for not completing homework on Wednesday, said a police officer.
Returning home, he developed high fever and was admitted to a hospital.
Later, he revealed that he was thrashed by the teacher.
A complaint was lodged at Vivek Vihar police station, which was later transferred to Anand Vihar police station, a senior officer said.
A police team went to Hedgewar hospital where the boy was admitted.
The accused, a guest teacher in the school, is on the run, the officer said.
The boy lives with his family, including his differently abled father, in Jwala Nagar area.
