Leifer, who also holds Israeli citizenship, was extradited to Australia from Israel in 2021 after fleeing in 2008 when the accusations surfaced.
During a sentencing hearing on Thursday, Victoria County Court judge Mark Gamble set a non-parole period of 11 years and six months but said he would take the 2,069 days she already served into account.
The two sisters and another sibling, Nicole Meyer, had accused Leifer of sexually abusing them on the grounds of the school in Melbourne, in locked staff offices, on school camps and at Leifer's home between 2003 and 2007, when they were teenagers. A jury found Leifer guilty of offences against Erlich and Sapper.
According to an indictment, Leifer assaulted one of the sisters in 2006 after inviting her home to "sleep over for kallah lessons" - a kind of pre-wedding etiquette class that includes sexual education.
On other occasions, Leifer told the students she was preparing them to be wives, prosecutors told the court earlier this year.
Sisters Nicole Meyer, Elly Sapper, and Dassi Erlich leave court after the sentencing on Thursday (Photo: Getty)
"This will help you for your wedding night," Leifer allegedly said after one sexual assault.
Gamble said the sisters had endured a "cruel and frightening upbringing at the hands of a very abusive mother," received no sex education and did not recognise sexualized conduct.
Addressing the court, he added: "This case is striking for just how vulnerable each of the two victims was and for the calculating way in which the offender, Mrs Leifer took callous advantage of those vulnerabilities in order to sexually abuse them for her own sexual gratification.
"This is a serious aggravating feature in respect of all of the offences.”
The court heard how school was part of a reclusive Jewish sect on the outskirts of Melbourne. "It was a life in which Jewish laws and customs were very important and strictly adhered to," Gamble added.
The Tel Aviv-born mother of eight maintains her innocence and Gamble said she had shown no remorse.
Leifer chose to watch her sentencing hearing by a video link from a high-security Melbourne women's prison rather than attend court in person. She is the prison's only Jewish inmate.
She began teaching at the school in 2001 and returned to Israel in 2008 the morning after she was stood down from her principal role because the allegations had come to light.
Australian police filed criminal charges in 2012 and the battle to extradite her from Israel which tested bilateral relations began in 2014. She returned in January 2021.
