Cellphone video shows a mother board a Gwinnett County school bus and hit one of her 15-year-old daughter’s classmates, officials said.

Nijah Underwood, 35, was arrested at her home on charges of simple battery and disruption of schools, according to jail records.

The charges stem from an incident that started Wednesday morning with a fight between Underwood’s daughter and another student at the bus stop, according to a Gwinnett police incident report.

After the fight ended, the student remained at the bus stop and the daughter went home, Central Gwinnett High School principal Shane Orr said in a letter to parents.

She returned to the bus stop with Underwood, officials said.

Despite the bus driver’s efforts to stop them, “that student and her parent boarded the bus and confronted the other student and a physical altercation ensued,” Orr said.

Police ultimately broke up the fight.

“This type of behavior — by the students and the parent — is unacceptable, and I want to assure you that we are taking appropriate action,” Orr said.

Both students, who are freshmen at Central Gwinnett High, face disciplinary action and battery charges, according to police and school officials.

“It was pretty bad,” student Jaleel Kyon told Channel 2 Action News after recording the fight. “They were jumping over seats and everything.”Underwood was released on bond Thursday.