Indiainfo-icon arrested a teenager on Wednesday for allegedly slitting the throat of a seven-year-old schoolmate in hopes the murder would lead to an exam being postponed, federal investigators said.

The 16-year-old is accused of killing his young schoolmate in September at a smart private school near Delhi in an attempt to delay an impending test and parent-teacher meeting.

Police had initially detained a bus conductor over the murder, claiming he killed the boy after the young pupil resisted a sex attack.

But a spokesman for federal investigators said they had credible evidence against the "academically weak teenager, whose motive was to postpone the examination and a forthcoming parent-teacher meeting".

 "He admitted during questioning that he wanted to shut the school to defer the exams and meeting," Central Bureau of Investigation spokesman R.K. Gaur told AFP.

The teenager, who cannot be named for legal reasons, would be sent to a juvenile detention centre until his trial for murder, he added.

Gaur said the bus conductor would remain in custody until cleared by a courtinfo-icon of any wrongdoing.