Malka Leifer, 56, was convicted on 18 counts - including rape - of sisters Dassi Erlich and Elly Sapper.

They have chosen to identify themselves in the media.

Leifer was acquitted of nine charges, including five that related to another sister, Nicole Meyer.

A court heard she abused Ms Erlich and Ms Sapper between 2003 and 2007 at the Adass Israel School, an ultra-Orthodox school in Melbourne where she was head of religion and later principal.

Prosecutor Justin Lewis said Leifer tended to have a sexual interest in girls when they were teenage students and took advantage of their vulnerability, ignorance in sexual matters, and her own position of authority.

The allegations first emerged in 2008 after Leifer had returned to her home country of Israel.

She fought against extradition to Australia but was returned to Melbourne in 2021. Her trial began in February and she pleaded not guilty to all 27 counts.

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The sisters had an isolated upbringing in the ultra-Orthodox Jewish community and received no sex education, the court heard.

They were around 12, 14 and 16 when Leifer starting teaching at the school in 2001.

Leifer was alleged to have abused Nicole Meyer while they shared a bed at a school camp as Ms Erlich pretended to be asleep in the same room.

Ms Erlich told the jury she had tried to form a relationship with another teacher to ask about what Leifer was doing, but Leifer discouraged her.

Leifer "told me it wasn't healthy for me to have a connection with another teacher, to have more than one mentor", Ms Erlich testified.

Ms Meyer told reporters outside court a guilty verdict was "all we've ever wanted".

"Since we started this battle, since we gave our police statements in 2011, to hear the word 'guilty' is what she has fought not to be for so many years, and what we have fought for so many years to prove," she said.