News outlets quote a Gwinnett County Schools police report as saying cellphone video shows 35-year-old Nijah Underwood hitting the girl's face.
Central Gwinnett High School principal Shane Orr says in a letter the two students got into a fight at a bus stop. One boarded the bus when it arrived while the other went home to get her mother. The mother and daughter confronted her despite the bus driver's efforts to stop them.
Jail records say Underwood was arrested on battery and school disruption charges. She was released on bond Thursday after Wednesday's fight. Both students were charged with battery.
It's unclear if the accused have lawyers.
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