Const. Dennis Rivest of the London Police Service said the eight girls were arrested Thursday.
Police said an investigation revealed that the victim had been the target of physical and emotional bullying, and cyberbullying.
The arrested girls face charges of criminal harassment.
Police said information about the bullying came from individuals who came forward in person and through an anonymous reporting web portal, called "South Cares," which is on the London South Collegiate website.
Bill Tucker, director of education at Thames Valley District School Board, said they had 70,000 community members take a pledge last year to end bullying.
"We know that the research says if an individual intervenes in bullying behaviour, we can stop bullying behaviour within seconds ...in 50 per cent of cases," he said.
Tucker added that school boards know they need help to end bullying, especially cyberbullying.
"It is such a complex, intricate challenge for school boards that we went to community and said, 'We need your help.'"
"If we can change behaviours about drinking and driving, if we change behaviours and attitudes around smoking, why can we not change behaviours and attitudes around bullying."Suggest a correction