Revd Alan Morris, 64, committed the offences while handing out punishments at a Catholic grammar school in Manchester between 1973 to 1990.
He was working as a teacher at St Ambrose College in Hale Barns, which was then run by the Christian Brothers Holy Order.
Manchester Minshull Street Court heard how Morris had a "fearsome reputation" as a strict disciplinarian and would sometimes seek out children to punish.
He was arrested in November 2012 following a complaint to the police from a young person who said he was abused during a 'punishment' but Morris continues to deny the allegations.
He told police the accuser was "a very good actor".
Morris denied all the charges and continues to maintain his innocence.
The court heard how he told police he was homosexual but could not act on it because of his vow of celibacy.
Morris was convicted earlier this year of 19 offences of indecent assault and inciting a child to perform an act of gross indecency.
This month, at a second trial, he was cleared of other alleged historic offences relating to two boys, while the jury didn't reach verdicts on eight others.
Detective Chief Inspector Chris Bridge, from Greater Manchester Police said: "For decades Morris displayed a veneer of total respectability: a science teacher in a well-respected and high performing school and latterly as a deacon of the church.
"Today he has been unmasked as a persistent and prolific sex offender.
"A self-proclaimed 'chief policeman', I have no doubt that he revelled in his fearsome reputation, taking it upon himself to seek out and punish pupils, using corporal punishment to cloak his real motive for chastising young boys: sexual gratification.
"His campaign of abuse lasted the best part of 20 years and has had a deep and lasting impact on his victims.
"We were absolutely taken aback by the sheer scale of his offending, which happened over so many years and involved so many boys and I must credit those who came forward to report what happened to them.
"Because of their actions he has finally been brought to justice, however I have no doubt there are others out there still that we do not know about.
"We understand how difficult it is to open up about such offending and a person can only do so when they are truly ready.
"To them I say that if you can find the strength to talk to us, we will treat your case with empathy and sensitivity."