The driver, an Italian national originally from Senegal, reportedly claimed he set the bus on fire in protest over migrant deaths at sea.
A Milan court sentenced Ousseynou Sy after he was found guilty of forced confinement with terrorist intent and prosecutors had demanded the 24 year sentence, according to Italian news agency ANSA.
Sy had driven his school bus with 51 pupils aged 12 and 13 on board towards Milan airport in March last year as he was transporting them to school in Crema, east of Milan.
Police blocked the bus and the children managed to escape through a back window that had been smashed by security forces.
Sy said at the time he had heard the voices of drowned migrant children urging him to take action, according to media reports.
Two of the children on the bus, who had Egyptian and Moroccan nationality, were given Italian citizenship in 2019 in recognition of their bravery in calling for assistance and helping others escape during the hijacking.
“We all condemn deaths at sea, but he kidnapped children of immigrants and we don’t believe he did it in protest,” the mother of one of the boys said.