The Saskatchewan Court of Appeal increased Kelley Minogue's sentence, which was originally two years, in written decision earlier this week.
The 39-year-old divorced mother was sentenced in June after pleading guilty to three counts of sexual interference stemming from 2010.
Crown prosecutor Sheryl Fillo appealed the sentence, arguing it wasn't consistent with similar rulings and calling it a series of major sexual assaults over a four-month period.
Justice Georgina Jackson noted Minogue's actions weren't a momentary lapse in judgment.
She pointed out that Minogue hosted the drinking parties at her home in Warman, north of Saskatoon, where the assaults happened, bought the teens alcohol and had sex with one of them on three separate occasions.
"I have spoken to one of the parents since the decision came down. They were extremely pleased and relieved at the result," said Fillo, who had recommended Minogue be sentenced to 3 1/2 years.
But Jackson ruled three years is appropriate. In her decision, she mentioned how Minogue has been punished in other ways, including the complete loss of a relationship with her children.
Jackson also believes the sentence will "fall more harshly" on her compared to other offenders serving similar sentences.
Minogue is currently in an Edmonton prison receiving sex offender treatment for women, therefore isolated from her parents, who Jackson described as her "primary source of support."
She apologized in court for her "inappropriate behaviour.''
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