A violent attack on board an MTA bus last week injured two teen sisters.

Natalie Allen says her 14- and 16-year-old girls were attacked by a group of students while riding the bus home Friday, March 16. Cellphone video shows the attack.

Allen says the group has a history of bullying her daughters at the New Visions Charter High School for Advanced Math & Science. She says the group attacked the sisters before they boarded the bus, and then got on the bus at West 231st Street and Riverdale Avenue to continue the beating.

Allen says she took her girls to a nearby hospital after the attack. She also filed a police report.

"My oldest, her braids were ripped out from her head and from the back...both of their lips are busted," she says, adding that one of the girls has a black-and-blue bruise on the side of her face.

A school representative says they do not comment on specific incidents, but "we take bullying and similar behavior seriously and investigate allegations that are brought to our attention."