The investigation concerns monks who taught at the Fort Augustus Abbey school in the Highlands in the 1960s and 70s. The school is now closed.
Police said they have been investigating since March following a report from a former pupil and further allegations came to light in a BBC documentary.
Charity Children 1st has set up a dedicated support line for anyone affected to contact them.
An 80-year-old man was charged in September and three men have now been reported to the procurator fiscal, police said.
A force spokesman said: "In relation to the investigation into historical physical and sexual abuse at Fort Augustus Abbey, Police Scotland have interviewed and spoken with a number of victims and witnesses of abuse and as a result have reported three men to the Crown Office and Procurator Fiscal Service.
"This is very much an ongoing investigation which was initiated by Highland and Islands division in March 2013 and has extended to liaison with a number of law enforcement agencies both across and out with the UK.
"We understand that it is very difficult for victims of abuse to speak about their experiences and a helpline run by Children 1st is available to provide support and advice to those who may be affected by the investigation."
Children 1st traditionally helps children, young people and families recover from abuse, neglect and violence, and campaigns for children's rights.
The helpline number is 0800 345 7457.