Of the convicts, Munshi Mohamamd Shohag, 35, son of Munshi Rezaul Karim of Dayarampur in Kumarkhali upazila, received the death sentence. He is the nephew of victim Munshi Rabiul Islam.
Raju Ahmed, 35, son of Majibor; Rubel, 35, son of Yakub; and Azad, 40, son of Hatem Sheikh of the upazila were given life imprisonment and fined Tk 20,000 each.
According to the prosecution, Rabiul, the headmaster of Mahendrapur Government Primary School was shot dead by miscreants at his own residence at Doyarampur in Kumarkhali upazila on January 24, 2015.
His mother filed a case at Kumarkhali Police Station.
Police pressed charges against four people on April 30, 2016.
After examining records and witnesses, Kushita District and Sessions Judge Arup Kumar Goswami announced the verdict.