The boy, son of Manikant, had left his home around 10am on Wednesday, and his body was found in the bamboo bush, about 200 metres from his house, police said.
Ravishankar, a student of Class 2, is believed to have been killed by close relatives over a land dispute, Purnia superintendent of police (SP) Amit Lodha said.
Terming the incident "unfortunate," the SP said the killers would be arrest soon.
"Most such incidents are related to land disputes," Lodha added.
The Dhamdaha deputy superintendent of police was investigating the matter and the raids were on to arrest the culprits, the SP said.