Acoording to google minumum is 77% and max is 100%, it varies depending on the place.
On Do Something.org they say 3.2 million kids are victims of bullying each year in the U.S. The percent would depend on what grades you want to explore. Do Something states that 90% of 4th through 8th graders report being victims of bullying, which must be when bullying is the worst.