John Farrell (73) and Paul Kelly (63) were charged with sexual and physical abuse of more than 20 ex-pupils of St Ninian’s School between 1977 and 1983.
Farrell was found guilty of four charges and Kelly was convicted of seven in charges which involved five victims.
They had denied a total of 51 counts of physical and sexual abuse at the school.
The pair committed indecent acts on boys aged 11 to 16 and forced the children to perform sex acts on them, the High Court in Glasgow heard. They punished the children by forcing them to stand naked in a hallway.
The trial, before judge Lord Matthews, began in April and was one of the longest abuse trials ever heard in Scotland. Dozens of the alleged victims gave evidence have given evidence, some of whom are now in their 50s.
Farrell, from Motherwell, and Kelly, from Plymouth, Devon, were remanded in custody and will be sentenced next month.
The four-year investigation into sexual and physical abuse at the former St Ninian’s School in Falkland uncovered a catalogue of offending on a massive scale.
Around 35 victims were involved, although not all of them gave evidence.
Men now in their 50s - many of whom had never spoken of their ordeal - told of the abuse they suffered at the hands of Farrell and Kelly.
They were assaulted with a variety of implements, including shoes, belt and a ruler and indecently assaulted.
Chief Inspector Nicola Shepherd, who led the investigation, said neither man had admitted any responsibility for their crimes when they were first spoken to by police.
“I’m very confident that both men knew what they were doing,” she said.
“There was a culture of violence and intimidation in the school. The boys didn’t speak out about it for fear of not being believed.
“The Christian Brothers were there to educate the boys; to care and protect them, but they committed the most appalling abuse.”
Chief Inspector Shepherd said that the impact on the victims was ‘profound’ because of the nature of the offences and the fact that they remained hidden for so long.
“It would have been difficult to lead a normal life after this,” she said.
“Many of the victims were vulnerable young boys who had been sent to the school by social workers or through the children’s hearing system.
“These men were in a position of trust and responsibility and they took advantage of their position.
“They committed the abuse knowing it would stay hidden.”
St Ninian’s opened in 1957 and closed in 1983.
It was run by the Christian Brothers, a Catholic religious order founded in Ireland in 1802 by a wealthy businessman for the purpose of educating poor Catholic boys. In the early 2000s, its reputation was marred when widespread abuse was uncovered in Ireland.
The building is now occupied by Falkland School, an award-winning facility for youngsters on the autistic spectrum.