Judge Md Kabir Uddin Pramanik of Gopalganj Childrens' Court passed the order at noon.
The convict was identified as Shah Alam Shikdar,14, a class VII student of Prince Shashi Kamal Biddapith and son of Badsha Shikdar, resident of Puishor village in the upazila.
According to the case statement, Shah Alam locked into an altercation with his classmate Barkat Ullah Prince over the seating arrangement at a local coaching center on September 12, 2017.
During school hours around 10am, Shah Alam lured Barkat to a nearby toilet through another classmate Sajib and stabbed him in his abdomen, leaving him dead on the spot.
Later, father of the deceased Hanif Molla alias Dulu filed a case with Kashiani Police Station accusing Shah Alam and Sajib and three others as unnamed.
Investigation officer SI Shah Jalal of the police station submitted a charge sheet on November 25.
Taking 17 witnesses' accounts, the court passed the sentence and acquitted Sajib from the accusation.