Horacio Corbacho and Nicola Corradi, as well as a gardener, were found guilty of rape and abuse at the school in Mendoza province from 2004 to 2016.
Several victims were in court to see sentence passed on Monday.
The case has shocked Argentina, Pope Francis' homeland, with many accusing the Church of acting too slowly.
The Catholic Church has faced an avalanche of child sexual abuse accusations around the world in the last few decades.
On Monday, the court in the provincial capital Mendoza sentenced Argentine priest Corbacho to 45 years in prison.
The 59 year old was found guilty of sexually abusing children at the Instituto Antonio Provolo de Mendoza in the city of Luján de Cuyo.
Corradi, an 83-year-old Italian national, was given a 42-year sentence.
He had been investigated for abuses at the institute's school in Verona, Italy, in the 1970s, but was never charged.
Armando Gómez, the gardener at the Luján de Cuyo school was jailed for 18 years.
The sentences cannot be appealed against.
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