Additional Metropolitan Sessions Judge SM Ashikur Rahman delivered the verdict.
Mohammad Rocky was sentenced to death while Nazrul, Rabiul, al Amin, Milon and Mujib Hawladar got life imprisonment.
The court also acquitted two other accused — Ibrahim alias Bahadur and Mohammad Hasan — as allegations brought against them could not be proven.
According to the prosecution, Mafizul Islam Bappi, 16, a ninth grader of Platinum Jute Mill School in Khalishpur was beaten to death by some miscreants while he and his friend Raju were sitting on the school premises on October 10, 2010.
Hafizur Rahman, brother of Bappi, filed a case at Khalishpur Police Station the following day.
On March 31, 2012, police submitted chargesheet against eight people.
Read Also: One to die for killing man in Sunamganj