One of the female students accused of assaulting a fellow student during a biology class in October has pleaded guilty to the crime.
The 17-year-old girl pleaded guilty to misdemeanor battery and will be sentenced at a later court date, according to the Chicago Tribune.
The other aggressor, her 18-year-old big sister, was also charged, according to the Tribune.
The fight, caught on tape, took place Oct. 6 at Roger C. Sullivan High School, 6631 North Bosworth Avenue.
In the video, 14-year-old Jillian Salgado struggled to break free of her two attackers. At one point, the assailants appear to slam her head off a table.
Salgado suffered a concussion, a neck sprain and several scratches and bruises.
The sisters, who skipped their expulsion hearing, were suspended from the high school and are now awaiting trials.