An elite Sydney private school teacher who preyed on a teenage girl seeking help with her science studies has been jailed for almost four years.
Ben Fenner turned the conversation sexual when the 17-year-old girl messaged him on Whatsapp.
Having noticed marks on her neck when she'd walked into class that day, he asked her what she liked sexually.
"All the messages on here are encrypted ... great for secrets," he told her.
Grooming her over months, he repeatedly met her for sex, including in his car parked near her home.
District Court Judge Robert Webber on Friday said the crimes required the court's "unequivocal denunciation" and jailed the 35-year-old for three years and nine months.
He said the offending had had "powerful and devastating effects" on the teenaged victim, who'd been entitled to expect her teacher would assist her with her studies.
"These legitimate expectations were cruelly dashed," the judge said.
"(Instead) he used her for his own sexual gratification."
After the teen reported the conduct to police, Fenner pleaded guilty to seven counts of sexual intercourse with a person aged under 18 in his care.
He also admitted a further eight instances of sexual intercourse.
Judge Webber took into account the former teacher's contrition and remorse for the offending and said the risk of reoffending was low.
But he knocked back a plea for leniency over the former teacher's good character and clean criminal record, saying Fenner's high standing in the community was what allowed him to teach at the elite school and thus prey on his victim.
The former student tightly gripped a friend's hand in court and became emotional after Fenner was led away.
In an earlier hearing, she stared him down from the witness box and told the court how it took her a long time to realise she'd been "used" by Fenner.
"I thought this was a normal thing ... a normal relationship," she said.
"I feel you have taken so much away from me ... my friends and high school experience."
Fenner will be eligible for release in January 2023.