Sarah Elizabeth Collins was a mentor and confidante to the female student as her PE teacher and soccer coach for years before she first molested the teen.
While initially seeing each other in secret, the pair become open about their relationship once the girl turned 16 and the teacher divorced her husband.
The victim, who cannot be legally named, went to the police in 2021, years after she had broken up with Collins. The teacher was arrested in September that year.
Collins was sentenced at Sydney's Penrith District Court on Friday after Judge Sophia Beckett found the pair had become sexually involved before the victim turned 16 and was able to legally consent.
"The relationship was kept secret at this point no doubt because of the victim's age (and) the offender's profession," the judge said.
Judge Beckett said Collins' repressed sexuality was one cause of the crime after reading a letter from her twin sister.
"Due to our upbringing, it was so hard for her to be comfortable about being open about her sexuality," the sister told the court.
This "state of personal crisis" merged with mental health conditions such as depression and anxiety, which she self-medicated through alcohol when she committed the abuse, Judge Beckett said.
"The personal struggle of a person confronting and acknowledging to others their sexual orientation in a predominantly heteronormative society should not be underestimated," she said.
In a victim impact statement, the student said her innocence had been corrupted and she had a "misplaced sense of shame" over her interactions with Collins which commenced when she was "emotionally vulnerable and easily influenced".
A jury found the teacher guilty in March this year of 17 charges of sexual misconduct with an underage person, including aggravated indecent assault.
The acts involved kissing, touching and other sexual acts conducted both at Collins' and the student's home.
Only one of the offences was committed while Collins was the girl's teacher, with the remainder occurring after the teen had moved to another school.
The offending was an abuse of trust and authority, Judge Beckett said, noting that although what happened may have been consensual after the student turned 16, there was no excusing the teacher's conduct before that age.
"The law draws a line in the sand and recognises that a person under this age is assumed to be too young to handle the physical act and potentially the psychosocial ramifications of engaging in such activity," she said.
However, the judge found that Collins was not a predator or pedophile and did not initially act as mentor to the young girl with an intention of becoming romantically or sexually involved.
Judge Beckett sentenced Collins to a maximum jail term of 30 months with a non-parole period of 15 months to send a message of deterrence to society.
"Schools ought to be a place where a parent can send their child knowing they will be protected by teachers," she said.
Collins will be eligible for parole in January 2025.
1800 RESPECT (1800 737 732)
National Sexual Abuse and Redress Support Service 1800 211 028
Fullstop Australia 1800 385 578
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