Moinuddin, a student of K L International Public School, was kidnapped on February 20 by his friends Vishal, Rahul and their associates, DIG police J N Singh said.
Later, the accused called the victim's father and demanded Rs 50 lakhs ransom, he said.
The shocking incident came to light when one of the kidnappers, Rahul Agarwal, committed suicide on Friday after being interrogated by the police.
The suicide note recovered from him revealed the involvement of the main accused Vishal, Singh said.
Vishal confessed to his crime after being interrogated and later the victim's body was recovered from the nearby forest of Hastinapur, he said.
The police is trying to nab the other friends involved in the crime as revealed by Vishal, he said.
It is suspected that the main reason behind the kidnapping and murder was personal enmity rather than ransom money, the police said.
In another incident, a school boy, Akshay, a resident of Saket here was kidnapped and killed by his friends, police said.