Police said the boy was charged because one of the girls in the video was being cyberbullied.
"That caused the victim to basically not be able to use her own Facebook [page] without feeling bullied or stressed," said Peel Regional Police spokesperson Const. Erin Cooper.
Schools and police forces across the country are being extra-sensitive to accusations of cyberbullying in the wake of some recent incidents, including the death of 15-year-old Amanda Todd of Port Coquitlam, B.C.
Todd committed suicide in October after being blackmailed, bullied online, and physically assaulted.
"Cyberbullying is definitely something that's creeping up," said Cooper.
But the Mississauga boy's mother told CBC News on Friday that her son is now being bullied by police and the local school board.
The incident that has caused such a furor took place on Dec. 17, when her son recorded a video of the fight which took place off school property — and then later posted it online.
Two days later he was called to the principal's office where he says he was arrested, handcuffed and put in a police cruiser.
"I started crying because I was so shocked," the boy said. "And then we walked out the front door to the car, and he put me in handcuffs."
Police couldn't contact his mother right away so, he says, he was put in a cell. "I was, like, really scared."
His mother believes police and the school went too far.
"If they wanted the outcome to be beneficial — or a learning process for all, as a society as a whole — I think they could have managed it in a better way than going to this extreme," she said.
The boy, who can't be identified because of his age, was charged with mischief and will appear in court in January.
In the meantime, he has also been suspended from school for a month and will be transferred to another school.