During the period 1967-1996, August M. committed violent and sexual attacks on his students while head of a Catholic boarding school run by Kremsmünster Abbey in Upper Austria.
He used a bull whip, hands and feet while beating students. He specialized in a two-handed slap to the head. Additionally, he threatened students with a shotgun, and sometimes ordered the students to beat up one of their number without repercussions.
He was also found guilty of sexually abusing 15 children whilst head of the school.
In November, August M. appealed to the high court against a custodial sentence of 12 years imposed in 2013. His appeal, based on a statute of limitations defence, was denied.
A special examiner appointed by the court will determine whether the former priest is able to serve the sentence as directed.
On Thursday, the 81-year-old walked slowly into court with the help of a cane, wearing a dark suit.
"I hear poorly, I do not understand everything now. If I can not follow, please be patient with me, I'm groggy," he said at the beginning of the trial to the chief judge.