Judge Timothy Spencer, who sentenced the shamed 70-year-old former deputy head, said he must have enjoyed a sense of complete power over the girls he abused.
He touched at least two girls in a store cupboard, his trial at Nottingham Crown Court was told.
One of those he held a particular “maligned power over”, said the judge.
Caffrey had asked her to stay behind, leaving her isolated and helpless.
He abused her when she was effectively trapped in the storeroom with him.
The popular teacher then repeatedly raped her at his Wollaton home, when her mother volunteered her for chores, the jury had heard.
Caffrey, a former well-built rugby player, was to strike again years later, raping a 19-year-old woman who visited his marital home in Stanton-on-the-Wolds.
The judge said once again Caffrey had engineered a situation on the pretext of helping him with chores.
The teenager was invited upstairs, pinned down on the martial bed, overpowered and raped – although he insisted later to police what happened was consensual.
The victim went to police 22 years ago but no charges were brought.
Judge Spencer said she was “let down” by the attitudes of society and the legal system.
Jurors heard how her case had remained forgotten until recently when more victims went to police.
“She was let down 20 years ago but, in my judgement, she has not been let down again,” said Judge Spencer.
He said Caffrey had deliberately targeted the victims, many who were in court to see him punished.
The judge concluded Caffrey had calculated they were ripe for this sort of abuse and calculated, for various reasons, they would not tell.
“The classroom and school was a place where they must have felt safe or secure, they must have felt anything but,” he stressed.
Caffrey, of Sandesquoy, Tankerness, Orkney, was found guilty of three rape charges and 12 indecent assaults, but was cleared on two indecent assault allegations.
The judge passed a total sentence of 17-and-a-half years on all charges and ordered Caffrey sign the sex offenders’ register. He is automatically barred from working with children.
The jury, who spent more than 24 hours deliberating over several days, made the unusual move of sending a note to the judge, which expressed their admiration for the victims who were clearly upset in court.
The letter ended: “We hope this verdict brings some closure to the victims.”
Judge Spencer thanked them for working assiduously and made them exempt from jury service for ten years.
“In my judgement you enjoyed that power and exploited it shamelessly,” said the judge on Thursday afternoon.
The court had heard how Caffrey put his hand up girls’ skirts as they read at his large desk at North Gate Primary School, in Old Basford, where he previously taught boys and girls.