Tusshar, 16, was found unconscious by some students in his school bathroom and was taken to a hospital on February 1.
He was later referred to the GTB Hospital where he was declared dead on arrival.
Three students were apprehended in the case on Friday, while one juvenile was on the run. He has now been apprehended from Khajuri Khas, police said.
CCTV footage revealed that some students went after Tusshar to the washroom, they said.
The accused students allegedly punched Tusshar in the neck and face. According to the police, it was suspected that the student died of internal injuries sustained during the scuffle.
Police said they are probing whether other students were also involved in the scuffle.
Family members of the deceased alleged that their son was thrashed by the students, the official said.
On the basis of complaint by the boy's family, a murder case was registered on Friday.
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