Toby Sendel doesn't know why she was bullied, but she knows the toll it took on her.

"It was a hard, traumatic experience that will leave a scar on me for the rest of my life," said Sendel, 18, who recently graduated from Royal Vale School in Montreal's west end.

When she was in high school, Sendel said, a group of "mean girls" would routinely make fun of her, call her names, throw her belongings on the floor and sometimes push her around.

In the school bathrooms, Sendel said, crude notes were scrawled on the walls, calling her a "whore."

"I felt constantly attacked."

At the peak of the bullying, in her third and fourth years of high school, Sendel said, students posted videos to social media, warning her they'd make her life a "living hell" if she showed up for school.

She said she also received death threats.

"I didn't feel safe," said Sendel, who barely went to class.

The bullying made her anxiety problems worse, and Sendel said she spent a good part of her time in the guidance counsellor's office or at home.

"I would try everything not to go to school," said Sendel, who had to repeat Secondary 3 because of her poor attendance record.

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Sendel said the bullying from other students left her feeling isolated and vulnerable.

She is far from alone.