The body of Nitin, a student of class 4, was found near Rein Basera area on August 27, they said.
His father Niraj, in his late-twenties and resident of Jhingurpura area, has been arrested for allegedly killing his son, who did not listen to him, they said.
"After investigation it became clear that the father has killed his son as he apprehended that the child was somebody else's," SSP Gulab Singh said yesterday.
Niraj gave the child Rs 2 to eat something so that he agrees to come to Rein Basera when he called him there from his school and strangulated him when he reached, he said.
He has been booked and sent to jail, the SSP said.