All the defendants had insisted they were innocent. They have two weeks to appeal. Their lawyers had argued that the linesman, Richard Nieuwenhuizen, had an underlying medical condition that contributed to his death, but Dutch forensic experts said he died as a result of the beating.
Judges said the young players acted together in the fatal beating and gave them the highest sentences available.
"The seriousness of the event, the lack of a clear reason for it, the terrible consequences, the fact that they haven't accepted responsibility for their acts and the enormous shock it caused throughout society and the entire football world meant that the minors received the maximum possible sentence," the court said in a statement.
The fatal attack took place Dec. 2 in the Dutch city of Almere, after the home team, Buitenboys, tied 2-2 with Nieuw Sloten, which is based in an Amsterdam neighborhood.
The 41-year-old Nieuwenhuizen was a volunteer linesman, officiating in a match in which his son was playing. He initially seemed to recover and shrugged off questions about whether he would file a complaint, but he later collapsed and died in hospital the following day.
The Netherlands' National Forensics Institute concluded he was killed as a result of injuries sustained during the attack.
In a statement, the court said the father had received a heavy punishment because "instead of setting a good example to the youths by criticizing their behavior he joined them in kicking and beating the linesman and has never accepted responsibility" for his actions.
Nieuwenhuizen's death triggered a bout of soul-searching in Dutch soccer and beyond about the loss of respect for sports officials among youth players.
More than 12,000 people attended a silent march for Nieuwenhuizen in Almere on Dec. 9.
Nieuwenhuizen's sons said Monday they hoped the convictions would send a message around the world that such attacks should not be tolerated in sport.