Former Calgary teacher Mario Joseph Denis Arsenault has been sentenced to eight years in prison for sexually assaulting and exploiting a female student who was in Grade 9 at the time of the crimes, which began in 2000. The sentence was handed down on Friday at the Calgary Courts Centre by Alberta Court of Justice Judge Francine Roy.
The victim, now an adult, cannot be identified due to a publication ban. Arsenault, who taught at École Sainte-Marguerite-Bourgeoys, a French-language school in southwest Calgary, was found guilty on November 17, 2025, of sexual assault and sexual exploitation. The incidents escalated from inappropriate behavior to a sexual relationship that continued after the student left the school.
Breach of Trust
Judge Roy emphasized the sacred and inviolable nature of teacher-student relationships, stating that Arsenault's actions constituted a betrayal of his student, his profession, and his educational institution. The judge noted that Arsenault abused his position of trust and authority, rendering the victim unable to provide meaningful consent despite being of legal age at the time.
In addition to the prison term, Arsenault was ordered to pay $3,750 in restitution to the victim and must have no contact with her. He is also required to provide a DNA sample for genetic analysis and will be listed on the sex offender registry for 20 years.
Lack of Mitigating Factors
Roy found no significant mitigating factors in Arsenault's favor. The judge described his earlier testimony as disconcerting and noted that he had failed to show substantive reflection on his actions. The loss of his teaching job and media coverage of the case were considered inevitable consequences of the crimes and did not influence the sentence.
During the trial in August 2025, the victim testified that the relationship began when Arsenault, then a first-year teacher, started having lunch with her and asking about her home life. Later, during a bus strike, he offered to drive her to and from school, a practice that continued even after the strike ended.
Calgary police alleged in May 2024 that Arsenault used his authority to groom the student for a sexual relationship. The proceedings on Friday were conducted in French, Arsenault's native language.
